Digital watermark embedding method, digital watermark embedding apparatus, and storage medium storing a digital watermark embedding program

ABSTRACT

A method for embedding a watermark into digital data, when the watermark is to be embedded in a digital image, independently changes real number components and imaginary number components of each of coefficient values of a complex watermark coefficient matrix using key, from the watermark to be embedded in the digital image, a step for performing a discrete Fourier inverse transform on the sequence matrix of the changed watermark and generating a watermark pattern; and a step for adding like tiling the water mark pattern to the original image, and generating an embedded image. 
     Further more, a watermark detection method for detecting a watermark from a digital data, a step for separating a block from an arbitrary position on the detected object image, a step for performing a discrete Fourier transform on the block and obtaining a sequence matrix, a step for generating position information for a component that is to be detected and that is specified by the key, a step for detecting a position marker sequence by calculating a phase difference of a sequence by an amount of parallel displacement, for each item of the position information, and extracting offset information which is the amount of parallel displacement when there is agreement between a start point of an embedded watermark and a start point of the block cut from the detected object image, and a step for detecting the embedded watermark cut from the detected object image.

RELATED APPLICATION INFORMATION

This application is a divisional application of prior application Ser.No. 09/443,239 filed Nov. 18, 1999 now U.S. Pat. No. 7,164,778, whichclaims the benefit of Japanese application Serial Nos. 11-016218 and11-016219, both filed on Jan. 25, 1999, all of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a watermark embedding method, watermarkdetection method, a watermark embedding apparatus, a watermark detectionapparatus, storage medium storing a watermark embedding program, storagemedium storing a watermark detection program, a watermark system, and aintegrated circuit, which, in order to actualize copyright protectionfor digital content, change personal information content by a smallamount that cannot be perceived, and embed watermark so that it cannotbe perceived by person, into said content.

2. Description of the Related Art

In recent years, the transfer of digital content via networks hasprogressed and been facilitated by technologies (such as the JPEG[‘Joint Picture Coding Expert Group’] method for digital informationsuch as voice, moving and still pictures. In addition, the distributionof content via networks has also begun to grow through informationinfrastructures such as the Internet.

However, content that is distributed via networks is digital informationand so it is easy to make perfect copies of personal content. Inaddition, with information infrastructures such as the Internet, allinformation users can become information transmitters and so there iscopyright infringement through the making and selling of illegal copies.Furthermore, the increase in the processing performance of personalcomputers facilitates the processing and editing of image and voice dataon personal computers, facilitating copyright infringement such asillegal secondary use and use that the authors had not envisaged. Thecurrent situation is that the growth of copyright infringement such asthis makes authors hesitant about supplying information and thusobstructs the distribution of information via networks.

In addition, separate from this, there is a problem from the point ofview of content providers in that “even if one wishes to handle therights to the content correctly, it is not possible to know where thoserights lie if one considers the possibility of incorrect usage” and thisalso prohibits the reuse of content.

As described below, copyright management/protection systems usingconventional technologies have been proposed with respect to these twoproblems.

Prior art relating to watermark technologies includes A. Piva et. al:“DCT-based Watermark Recovering with Resorting to the UncorruptedOriginal Image,” Proceedings of the 1997 International conference onImage Processing (ICIP'97) (Ref. 1 in the following); Takao Nakamura,Hiroshi Ogawa, Youichi Takashima: “A Watermarking Technique for StileImage,” NTT R&D Vol. 47, NO. 6, 1998 (Ref. 2 in the following); andWisetsuit Piyapisuit, Kineo Matsui: “Block Characteristic in Color ImageWatermaking Using Equivalent Signal Transform” National Conference ofthe Institute of Electronics, Information and Communication Engineers,D-11-42, 1999 (Ref. 3 in the following).

The method of Ref. 1 performs an orthogonal transform of an originalimage size obtains a frequency component matrix, and changes acoefficient value of a mid-frequency band in the frequency componentmatrix to embed the watermark. Changing the coefficient value isperformed by changing the contrast. This provides robustness withrespect to irreversibel compressing and color change, and also withrespect to changes in the contrast.

In addition, with the method of Ref. 1, when the watermark is read, animage which is to be investigated has the watermark read by inversespread of the coefficient values of the mid-frequency band in thefrequency component matrix obtained by orthogonal transform. Throughthis, it is possible to compare a magnification or reduction withdigital content at the original size, align it with the original digitalcontent and perform detection.

In addition, with the method of Ref. 1, when reading is performed, anattempt is made using a random number used in the spectral spread andthe read watermark is that for which the response is highest. This makesit possible to detect partial images and the like where it is not knownwhere a cut portion lies on the original digital content.

However, the above mentioned Ref. 1 involves the following problems.

I. There is a low robustness with respect to partial cutting.

II. There is a large amount of processing involved for an orthogonaltransform of an original image at the full size thereof, which causes alocal degree of complexity.

III. There is a great amount of image deterioration when the watermarkis embedded.

IV. Attempted reading is performed for all values obtained for thewatermark when the watermark is detected.

With the method of Ref. 2, an image is generally divided into largeblocks of a block size used by non-reversible compression, an orthogonaltransform is performed for each block and a frequency component matrixis obtained and normalized. A sequence sequence that performs embeddingis then selected using a key, and an inverse orthogonal transform isperformed to obtain the image having an embedded watermark. With thismethod, there is robustness with respect to non-reversible compressingbut there are problems of color change, contrast change and a lowrobustness with respect to partial cutting. In addition, although thismethod aims to improve the image quality/robustness by normalizing andembedding weakly on flat portions and strongly on complex portions ofthe image, it does not function effectively. Changing the low-frequencyband improves the robustness.

When there is watermark detection using Ref. 2, processing is performedup to normalization when there is embedding, and the watermark isdetected from the key and the normalized frequency component matrix.This means that when the a block size is the same as the image size,there is robustness with respect to magnification and reduction.However, quantitative evaluations have not been performed for thereliability of the detected watermark. In addition, there is also aproblem of a large amount of image deterioration when the watermark isembedded.

With the method of Ref. 3, processing is implemented to take a transformmatrix of an equivalent signal transform (such a RGB<->YCbCr or thelike) for a color image and change it slightly in accordance withwatermark for something defined. Watermark information detection forRef. 3 involves performing an equivalent signal transform on thedetected object image and then using statistical values to detectwhether or not there is a special status due to the watermark. With thisdetection, the method of Ref. 3 has a robustness with respect togeometrical changes of the image. However, the method is extremely weakwith respect to non-reversible compression and color changes. Inaddition, when there is multi-bit embedding, the embedding is for onebit per block and so there is a problem that the robustness with respectto geometrical transformation is extremely weak.

SUMMARY OF THE INVENTION

Accordingly, it is general object of the present invention to provide awatermark embedding method, a watermark detection method, a watermarkembedding apparatus, a watermark detection apparatus, a storage mediumstoring a watermark embedding program, a storage medium storing awatermark detection program, a watermark system, and an integratedcircuit which can perform a high-speed embedding process even when thereis detection processing without an original image and it is not knownwhich portion of a partial image corresponds to the original image.

It is another object of the present invention it to provide a watermarkdetection method, a watermark embedding apparatus, a watermark detectionapparatus, a storage medium storing a watermark embedding program, astorage medium storing a watermark detection program, a watermarksystem, and an integrated circuit, which use a calculation method basedon visual characteristics, for the image's degree of local complexity,to enable a relative improvement in the robustness of a watermark.

The above objects of the present invention are achieved by a method forembedding a watermark so that it cannot be sensed by a person, whichmethod includes a step for, when the watermark is to be embedded in adigital image, independently changes real number components andimaginary number components of each of coefficient values of a complexwatermark coefficient matrix using key, from the watermark to beembedded in the digital image; a step for performing a discrete Fourierinverse transform on the sequence matrix of the changed watermark andgenerating a watermark pattern; and a step for adding like tiling thewater mark pattern to the original image and generating an embeddedimage.

According to the present invention, it is possible to independentlychange the real number components and the imaginary number components ofeach coefficient value of the complex watermark coefficient matrix, fromthe key and the watermark, perform a discrete Fourier inverse transformon the changed watermark coefficient matrix to generate a watermarkpattern, add like tiling a watermark pattern to an original image, andgenerate an embedded image.

In addition, the above objects of the present invention are achieved bya watermark embedding method which when embedding a watermark so thatcannot be perceived visually in a digital image, comprises a step fordetermining a degree of local complexity of an image, and, in accordancewith the degree of local complexity of the image, changes complexportions of the image more than not so complex portions, and obtains anembedded image.

According to the present invention, it is possible to create imagedegrees of local complexity that have relatively large values fortextured domains and relatively small values for smooth domains and edgeportions. This makes it possible to realize more adaptive informationmanagement for the visual characteristics than does the conventionalart.

In addition, the above object of the present invention are achieved by awatermark embedding method which, when embedding a watermark so that itcannot be perceived by visually in a digital image, comprises a step forgenerating a local degree of complexity of an image from inputinformation that is a digital image; a step for using key necessary forembedding to generate a watermark pattern from a watermark, a step foradding the watermark pattern to the input image in accordance with thedegree of local complexity of the image; and a step for generating animage in which the watermark is embedded.

According to the present invention, it is possible, when embedding, toadd a pattern that expresses a design of an original image, and soenable a further improvement to the image quality, that is, the relativerobustness.

In addition, the above objects of the present invention are achieved bya watermark embedding method which, when embedding a watermark so thatit cannot be perceived visually in a digital image, comprises a step fordividing a digital input image into blocks of a required size andgenerating a degree of local complexity of an image; a step for usingkey necessary for embedding to generate a basic watermark pattern whichforms the basis for the watermark; a step for generating an adaptivewatermark pattern that has orthogonal transform sequences correspondingto the basic watermark pattern emphasized in accordance with a value ofan amplitude of an orthogonal transform sequence of each block; a stepfor adding the basic watermark pattern and the adaptive watermarkpattern to the blocks in accordance with an emphasis parameter and thedegree of local complexity of the image; and a step for generating animage in which watermark pattern information is embedded.

As described above, according to the present invention, when there is awatermark embedding method of the type that divides an image intoblocks, changes a sequence matrix obtained by orthogonal transform ofthose blocks and embeds a watermark, the degree of local complexity ofeach block is used to switch in gradation between the two types ofwatermark patterns comprising, the basic watermark pattern and anadaptive watermark pattern created from a sequence matrix obtained fromorthogonal transform of the blocks, to obtain in image in whichwatermark pattern information is embedded. Hereby, a component valueimage obtained by handling edges and textures in the same manner,texture degree indexes obtained from the local density of theedge/texture component value images, and a texture component value imageobtained from these two are generated so that it is possible to create atexture component image that has a relatively large value for textureddomains and a relatively small value for smooth domains or for textureportions, thus realizing adaptive information embedding for visualcharacteristics to a greater degree than in the conventional art, andincreasing the relative robustness of the watermark.

In addition, the above object of on the present invention are achievedby a watermark detection method for detecting a watermark from a digitaldetected object image in which a visually imperceptible watermark hasbeen embedded therein, which method comprises a step for separating ablock from an arbitrary position on the detected object image; a stepfor performing a discrete Fourier transform on the block and obtaining asequence matrix; a step for generating position information for acomponent that is to be detected and that is specified by the key; astep for detecting a position marker sequence by calculating a phasedifference of a sequence by an amount of parallel displacement, for eachitem of the position information, and extracting offset informationwhich is the amount of parallel displacement when there is agreementbetween a start point of an embedded watermark and a start point of theblock cut from the detected object image; and a step for detecting theembedded watermark cut from the detected object image.

According to the present invention, it is possible to cut a block froman arbitrary position of a detected object image and then, once adiscrete Fourier transform has been performed on the block and asequence matrix obtained, take the correlation between a sequenceindicating the start point of a watermark pattern and a sequence for thephase difference of sequences according to the amount of paralleldisplacement of each item of the component value sequence, and soperform a search for an amount of parallel displacement, and, as aresult of that search, use the amount of parallel displacement when themaximum response value is output as the amount of parallel displacementfrom the start point of the watermark pattern to the start point of theblock cut from the start point of the watermark pattern as the amount ofparallel displacement, and then use this amount of parallel displacementto further detect an embedded watermark.

In addition, the above objects of the present invention are achieved bya watermark detection method for detecting a watermark from a detectedobject image that has a watermark embedded therein, which methodcomprises a step for detecting object image phase position informationfrom a key; a step for generating a position marker sequence from thekey; and a step for using detected position marker detection informationto detect offset information that indicates the degree of displacementbetween the start point of a watermark pattern when embedded, and astart point of a pixel block cut from the detected object image; andthat uses the offset information to detect a watermark embedded in theimage block.

According to the present invention, when there is a search for an amountof parallel displacement, it is not necessary to perform a discreteFourier transform for each scan as only one discrete Fourier transformprior to the search is sufficient and so it is possible to shorten thedetection processing time to less than is required for a simple searchfor the amount of parallel displacement (as in the method that performsan orthogonal transform while displacing coordinates and then scans).

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome more apparent from the following detailed description when readin conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram showing the configuration of an watermark embeddingapparatus according to the first embodiment of the present invention;

FIG. 2 is a flow chart showing the process of the watermark embeddingapparatus according to the first embodiment of the present invention;

FIG. 3 is a diagram showing the configuration of an embedding objectcomponent specification portion of the first embodiment of the presentinvention;

FIG. 4 is a flow chart showing the process of an embedding objectcomponent specification portion of the first embodiment of the presentinvention;

FIG. 5 is a diagram showing the configuration of an embedding sequencegeneration portion of the first embodiment of the present invention;

FIG. 6 is a flow chart showing the process of the embedding sequencegeneration portion of the first embodiment of the present invention;

FIG. 7 is a flow chart of the process of a component value changeportion of the first embodiment of the present invention;

FIG. 8 is a diagram describing the process of a discrete Fourier inversetransform portion of the first embodiment of the present invention;

FIG. 9 is a diagram describing the process of the watermark patternadding portion of the first embodiment of the present invention;

FIG. 10 is a diagram showing the configuration of a watermark detectionapparatus according to the second embodiment of the present invention;

FIG. 11 is a flow chart showing the process of the watermark detectionapparatus according to the second embodiment of the present invention;

FIG. 12 is a diagram showing the configuration of a detected objectcomponent specification portion according to the second embodiment ofthe present invention;

FIG. 13 is a flow chart showing the process of the detected objectcomponent specification portion according to the second embodiment ofthe present invention;

FIG. 14 is a diagram showing the configuration of a position markersequence generation portion according to the second embodiment of thepresent invention;

FIG. 15 is a flow chart showing the process of the position markersequence generation portion according to the second embodiment of thepresent invention;

FIG. 16 is a diagram showing the configuration of the position markerdetection portion according to the second embodiment of the presentinvention;

FIG. 17 is a flow chart showing the process of the position markerdetection portion according to the second embodiment of the presentinvention;

FIG. 18 is a diagram describing the process of a block generationportion according to the second embodiment of the present invention;

FIG. 19 is a flowchart showing the process of a block generation portionaccording to the second embodiment of the present invention;

FIG. 20 is a flow chart showing the process of a detected object-imageobject sequence generation portion according to the second embodiment ofthe present invention;

FIG. 21 is a diagram showing the configuration of a watermark detectionportion according to the second embodiment of the present invention;

FIG. 22 is a flow chart showing the process of the watermark detectionportion according to the second embodiment of the present invention;

FIG. 23 is a diagram showing the configuration of symbol detectionportion according to the second embodiment of the present invention;

FIG. 24 is a flow chart showing the process of the symbol detectionportion according to the second embodiment of the present invention;

FIG. 25 is a diagram showing the configuration of symbol sequencegeneration portion according to the second embodiment of the presentinvention;

FIG. 26 is a flow chart showing the process of the symbol sequencegeneration portion according to the second embodiment of the presentinvention;

FIG. 27 is a diagram showing the configuration of a detection resultgeneration portion according to the second embodiment of the presentinvention;

FIG. 28 is a flow chart showing the process of the detection resultgeneration portion according to the second embodiment of the presentinvention;

FIG. 29 is a flow chart showing the process of a block generationportion according to a third embodiment of the present invention;

FIG. 30 is a diagram describing the process of the block generationportion according to the third embodiment of the present invention;

FIG. 31 is a diagram describing the process of the block generationportion according to the fourth embodiment of the present invention;

FIG. 32 is a flow chart showing the process of the block generationportion of a position marker detection portion according to a fourthembodiment of the present invention;

FIG. 33 is a diagram showing the configuration of the watermarkdetection portion according to a fifth embodiment of the presentinvention;

FIG. 34 is a flow chart showing the process of the watermark detectionportion according to the fifth embodiment of the present invention;

FIG. 35 is a diagram describing the process of a block division portionaccording to a fifth embodiment of the present invention;

FIG. 36 is a diagram showing the configuration of a symbol detectionportion according to the fifth embodiment of the present invention;

FIG. 37 is a flow chart showing the process of the symbol detectionportion according to the fifth embodiment of the present invention;

FIG. 38 is a diagram showing the configuration of the symbol sequencegeneration portion according to the fifth embodiment of the presentinvention;

FIG. 39 is a flow chart showing the process of the symbol sequencegeneration portion according to the fifth embodiment of the presentinvention;

FIG. 40 is a diagram showing the configuration of a detection resultgeneration portion according to the fifth embodiment of the presentinvention;

FIG. 41 is a flow chart showing the process of the detection resultgeneration portion according to the fifth embodiment of the presentinvention;

FIG. 42 is a diagram showing the configuration of a watermark detectionportion according to a sixth embodiment of the present invention;

FIG. 43 is a flow chart showing the process of the watermark detectionportion according to the sixth embodiment of the present invention;

FIG. 44 is a diagram describing the process of a block division portionaccording to the sixth embodiment of the present invention;

FIG. 45 is a diagram showing the configuration of a symbol detectionportion according to the sixth embodiment of the present invention;

FIG. 46 is a flow chart showing the process of the symbol detectionportion according to the sixth embodiment of the present invention;

FIG. 47 is a diagram showing the configuration of a symbol sequencegeneration portion according to the sixth embodiment of the presentinvention;

FIG. 48 is a flow chart showing the process of the symbol sequencegeneration portion according to the sixth embodiment of the presentinvention;

FIG. 49 is a diagram showing the configuration of a detection resultgeneration portion according to the sixth embodiment of the presentinvention;

FIG. 50 is a flow chart showing the process of the detection resultgeneration portion according to the sixth embodiment of the presentinvention;

FIG. 51 is a diagram showing the configuration of the watermarkdetection portion according to the seventh embodiment of the presentinvention;

FIG. 52 is a flow chart showing the process of a watermark detectionportion according to the seventh embodiment of the present invention;

FIG. 53 is a diagram describing the process of a block division portionaccording to the seventh embodiment of the present invention;

FIG. 54 is a diagram showing the configuration of a symbol detectionportion according to the seventh embodiment of the present invention;

FIG. 55 is a flow chat showing the process of the symbol detectionportion according to the seventh embodiment of the present invention;

FIG. 56 is a diagram showing the configuration of a symbol sequencegeneration portion according to the seventh embodiment of the presentinvention;

FIG. 57 is a flow chart showing the process of the symbol sequencegeneration portion according to the seventh embodiment of the presentinvention;

FIG. 58 is a diagram showing the configuration of a detection resultsgeneration portion according to the seventh embodiment of the presentinvention;

FIG. 59 is a flow chart showing the process of the detection resultsgeneration portion according to the seventh embodiment of the presentinvention;

FIG. 60 is a diagram showing the configuration of a block generationportion of a position marker detection portion according to an eighthembodiment of the present invention;

FIG. 61 is a flow chart showing the process of the block generationportion of the position marker detection portion according to the eighthembodiment of the present invention;

FIG. 62 is a diagram describing the process of the block generationportion according to the eighth embodiment of the present invention;

FIG. 63 is a diagram showing the configuration of the block generationportion of the position marker detection portion according to a ninthembodiment of the present invention;

FIG. 64 is a flow chart showing the process of the block generationportion of the position marker detection portion according to the ninthembodiment of the present invention;

FIG. 65 is a diagram describing the block division of the blockgeneration portion according to the ninth embodiment of the presentinvention;

FIG. 66 is a diagram describing the process of a cyclic shift portion ofthe block generation portion according to the ninth embodiment of thepresent invention;

FIG. 67 is a diagram showing the configuration of a block generationportion of a position marker detection portion according to a tenthembodiment of the present invention;

FIG. 68 is a flow chart showing the process of the block generationportion of the tenth embodiment of the present invention;

FIG. 69 is a diagram describing the process of the block generationportion of the tenth embodiment of the present invention;

FIG. 70 is a diagram showing division processing of the block generationportion according to the tenth embodiment of the present invention;

FIG. 71 is a diagram showing the process of a cyclic shift portionaccording to the tenth embodiment of the present invention;

FIG. 72 is a diagram showing the configuration of a watermark detectionapparatus according to a an eleventh embodiment of the presentinvention;

FIG. 73 is a diagram showing the process of an watermark detectionapparatus according to the eleventh embodiment of the present invention;

FIG. 74 is a diagram showing the configuration of a detected objectcomponent specification portion according to an eleventh embodiment ofthe present invention;

FIG. 75 is a flow chart shoring the process of the detected objectcomponent specification portion according to the eleventh embodiment ofthe present invention;

FIG. 76 is a diagram showing the configuration of a position markersequence generation portion according to the eleventh embodiment of thepresent invention;

FIG. 77 is a flow chart showing the process of the position markersequence generation portion according to the eleventh embodiment of thepresent invention;

FIG. 78 is a diagram showing the configuration of a position markerdetection portion according to the eleventh embodiment of the presentinvention;

FIG. 79 is a flow chart showing the process of the position markersequence generation portion according to the eleventh embodiment of thepresent invention;

FIG. 80 is a flow chart showing the process of the detection objectsequence generation of the position marker detection portion accordingto the eleventh embodiment of the present invention;

FIG. 81 is a diagram showing the configuration of a watermark detectionportion according to the eleventh embodiment of the present invention;

FIG. 82 is a flow chart showing the process of the watermark detectionportion according to the eleventh embodiment of the present invention;

FIG. 83 is a diagram showing the configuration of a symbol detectionportion according to the eleventh embodiment of the present invention;

FIG. 84 is a flow chart showing the process of the symbol detectionportion according to the eleventh embodiment of the present invention;

FIG. 85 is a diagram showing the configuration of the symbol generationportion according to the eleventh embodiment of the preset invention;

FIG. 86 is a flow chart showing the process of the symbol generationportion according to the eleventh embodiment of the present invention;

FIG. 87 is a diagram showing the configuration of a detection resultsgeneration portion according to the eleventh embodiment of the presentinvention;

FIG. 88 is a flow chart showing the process of the detection resultsgeneration portion according to the eleventh embodiment of the presentinvention;

FIG. 89 is a diagram describing the process of the position markerdetection portion according to a twelfth embodiment of the presentinvention;

FIG. 90 is a diagram showing the configuration of the watermarkdetection portion according to a thirteenth embodiment of the presentinvention;

FIG. 91 is a flow chart showing the process of the watermark detectionportion according to the thirteenth embodiment of the present invention;

FIG. 92 is a diagram describing the process of a block division portionaccording to the thirteenth embodiment of the present invention;

FIG. 93 is a diagram showing the configuration of a symbol detectionportion according to the thirteenth embodiment of the present invention;

FIG. 94 is a flow chart showing the process of the symbol detectionportion of the thirteenth embodiment of the present invention;

FIG. 95 is a diagram showing the configuration of a symbol sequencegeneration portion according to the thirteenth embodiment of the presentinvention;

FIG. 96 is a flow chart showing the process of the symbol sequencegeneration portion according to the thirteenth embodiment of the presentinvention;

FIG. 97 is a diagram showing the configuration of a detection resultgeneration portion according to the thirteenth embodiment of the presetinvention;

FIG. 98 is a flow chart showing the process of the detection resultgeneration portion according to the thirteenth embodiment of the presentinvention;

FIG. 99 is a diagram describing the process of a block division portionof a watermark detection portion according to a fourteenth embodiment ofthe present invention;

FIG. 100 is a diagram showing the configuration of a block generationportion of a position marker detection portion according to a fifteenthembodiment of the present invention;

FIG. 101 is a flow chart showing the process of the block generationportion according to the fifteenth embodiment of the present invention;

FIG. 102 is a diagram describing the process of the block generationportion according to the fifteenth embodiment of the present invention;

FIG. 103 is a diagram showing the configuration of a block generationportion of a position marker detection portion according to a sixteenthembodiment of the present invention;

FIG. 104 is a flow chart showing the process of the block generationportion of the position marker detection portion according to thesixteenth embodiment of the present invention;

FIG. 105 is a diagram describing the process of the block generationportion according to the sixteenth embodiment of the present invention;

FIG. 106 is a flow chart showing the process of an offset informationgeneration portion of a position marker detection portion according to anineteenth embodiment of the present invention;

FIG. 107 is a flow chart showing the process of a detection resultsgeneration portion of a watermark detection portion according to atwentieth embodiment of the present invention;

FIG. 108 is a graph showing the theoretical values and the corr valuesaccording to a computer simulation of a twenty-first embodiment of thepresent invention;

FIG. 109 is a graph of symbol detect information according to a computersimulation of the twenty-first embodiment of the present invention;

FIG. 110 is a diagram showing the PSNR when the embedding intensity ofthe present invention is changed;

FIG. 111 is a diagram showing the results of using computer simulationof the present invention to detect watermark from an image containing awatermark;

FIG. 112 is a diagram showing the result of using computer simulation ofthe present invention to detect watermark from a partial image;

FIG. 113 is a diagram showing a failed detection and successful partialimage using computer simulation of the present invention;

FIG. 114 is a diagram showing detection results from a JPEG compressedimage using a computer simulation of the present invention;

FIG. 115 is a diagram showing a gray scale image (binary image) using acomputer simulation of the present invention;

FIG. 116 is an example of a composite image using a computer simulationof the present invention;

FIG. 117 is a diagram showing a configuration of a watermark embeddingapparatus according to a twenty-second embodiment of the presentinvention;

FIG. 118 is a flow chart showing the process of a watermark embeddingapparatus according to a twenty-second embodiment of the presentinvention;

FIG. 119 is a flow chart showing the process of an edge/texturecomponent value image creation portion according to the twenty-secondembodiment of the present invention;

FIG. 120 is an example of an input image and an edge/texture componentimage according to the twenty-second embodiment of the presentinvention;

FIG. 121 is a diagram showing the configuration of a watermark embeddingapparatus according to a twenty-third embodiment of the presentinvention;

FIG. 122 is a flow chart showing the process of the watermark embeddingapparatus according to a twenty-third embodiment of the presentinvention;

FIG. 123 is a flow chart showing the process of a texture degree indexcreation portion according to the twenty-third embodiment of the presentinvention;

FIG. 124 is a diagram describing the process of an up-sampler accordingto the twenty-third embodiment of the present invention;

FIG. 125 is a diagram showing an edge/texture component value image andtexture degree according to the twenty-third embodiment of the presentinvention;

FIG. 126 is a flow chart showing the process of a watermark embeddingapparatus according to a twenty-fourth embodiment of the presentinvention;

FIG. 127 is a flow chart showing the process of a texture degree indexcreation portion according to the twenty-fourth embodiment of thepresent invention;

FIG. 128 is a diagram showing the configuration of a watermark embeddingapparatus according to a twenty-fifth embodiment of the presentinvention;

FIG. 129 is a flow chart showing the process of the watermark embeddingapparatus according to the twenty-fifth embodiment of the presentinvention;

FIG. 130 is a flow chart showing the process of a texture componentvalue image creation portion according to the twenty-fifth embodiment ofthe present invention;

FIG. 131 is a diagram showing image input and output by each portion ofthe twenty-fifth embodiment of the present invention;

FIG. 132 is a diagram showing the configuration of a watermark embeddingapparatus according to a twenty-sixth embodiment of the presentinvention;

FIG. 133 is a flow chart showing the process of the watermark embeddingapparatus according to the twenty-sixth embodiment of the presentinvention;

FIG. 134 is a diagram showing the configuration of a watermark embeddingapparatus according to a twenty-seventh embodiment of the presentinvention;

FIG. 135 is a flow chart showing the process of the watermark embeddingapparatus according to the twenty-seventh embodiment of the presentinvention;

FIG. 136 is a flow chart showing the process of an adaptive watermarkpattern creation portion according to the twenty-seventh embodiment ofthe present invention;

FIG. 137 is a diagram showing a block and pattern in the processing ofembedding a watermark according to the twenty-seventh embodiment of thepresent invention.

FIG. 138 is a diagram showing the configuration of a integrated circuitaccording to a twenty-eight embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A detailed description of embodiment of the present invention will nowbe given with reference to the figures.

First Embodiment

This embodiment describes a first embodiment of watermark embedding.

FIG. 1 is a diagram showing the configuration of the watermark embeddingapparatus according to a first embodiment of the present invention.

The watermark embedding apparatus 100 is configured by a watermarkpattern adding portion 110, and embedding sequence generation portion120, an embedding object component specification portion 130, acomponent value change portion 140, and a discrete Fourier inversetransform portion 150.

The watermark embedding apparatus 100 inputs an input image 101, anintensity parameter 102, a watermark 103, and a key 104, and ultimatelyoutputs an embedded image 105.

The following is an outline of the operation according to the aboveconfiguration.

FIG. 2 is a flow chart showing the process of the watermark embeddingapparatus according to the first embodiment of the present invention.

Step 110) The watermark embedding apparatus 100 that has received theabove-mentioned inputs, first of all, in the embedding object componentspecification portion 130, uses the key 104 to generate embedding objectcomponent position information 131 which is sent to the component valuechange portion 140.

Step 120) In addition, in the embedding sequence generation portion 120,the key is used to disperse position marker information of the watermarkto from an the embedding sequence 121, which is sent send it to thecomponent value change portion 140.

Step 130) The component value change portion 140 uses the embeddingsequence 121 and the embedding object component position information 131from the embedding object component specification portion 130 to make aninitial value of a watermark coefficient matrix 141 the zero matrix.

Step 140) The component value change portion 140 changes the componentvalue of the watermark coefficient matrix 141.

Step 150) The discrete Fourier inverse transform portion 150 performs adiscrete Fourier inverse transform on the watermark coefficient matrixand creates the watermark pattern 151.

Step 160) The watermark pattern adding portion 110 uses the intensityparameter to emphasize the watermark pattern 151, and add like tilingthe watermark pattern to the input image 101, and outputs an embeddedimage 105.

The following description explains a description of the processing inthe embedding object component specification portion 130. FIG. 3 is adiagram showing the configuration of embedding object componentspecification portion of the first embodiment of the present invention.

In this figure, the embedding object component specification portion 130has a random number generator 132 that inputs the key 104 and generatesthe embedding object component position information 131.

FIG. 4 is a flow chart showing the process of the embedding objectcomponent specification portion according to the first embodiment of thepresent invention.

Step 111) The embedding object component specification portion 130inputs key 104 and uses the random number generator 132 to generate arandom number sequence that takes the key 104 as its initial value.

Step 112) The embedding object component specification portion 130 alsouses the generated random number sequence as the basis for generatingembedding object component position information 131 which is a sequencehaving a length the same as the length n of the embedding sequence whichwill be described later.

The embedding object component position information 131 is configured asdescribed below.L _(k)=(x _(k), y _(k), z _(k)) (0<=k<n)

-   x_(k): embedding object component sequence x-direction second    degree;-   y_(k): embedding object component sequence y-direction second    degree;-   z_(k): flag expressing real or imaginary for the embedding object    sequence (whether or not it is a real number component or an    imaginary number component)

In each item of the embedding object component position information 131,the embedding object component specification portion 130 avoidsduplication (all of the three components above must not be in agreementfor the two items L k and L m In addition, in order to compensate forthe addition of digital noise and irreversible decompression,

$\sqrt{x_{k}^{2} + y_{k}^{2}} < r$so that there is a bandwidth limit preventing sequences from beingselected from the high-frequency region. Furthermore, although signalsobtained from the discrete Fourier inverse transform become realnumbers, embedding which maintains a necessary symmetry of the sequencematrix,F(u,v)=F*(N−u,N−v)(where F(u,v) is a Fourier transform of the sample value f(x,y) (0<=x<N,0<=y<N) where N is the size of the length and width of the sequencematrix to be described later, and * indicates a complex conjugate),requires that only positive values be selected for the x-directionsecond degree or the y-direction second degree of the embedding symmetrysequence. The embedding object component position information 131 issent to the component value change portion 140.

The following is a description of the configuration of the embeddingsequence generation portion 120 in the present embodiment.

FIG. 5 is a diagram configuration of the embedding sequence generationportion of the first embodiment of the present invention. The embeddingsequence generation portion 120 has a spread sequence generator 122 thatinputs the watermark 103 and the key 104. Basically, the direct spreadmethod in spread spectrum communications is used as the basis.Specifically, the spread sequence generator 122 shown in FIG. 5,generates the embedding sequence 121 which is a real number sequence oflength n.

FIG. 6 is a flow chart showing the process of the embedding sequencegeneration portion of the first embodiment of the present invention.

Step 121) Position marker spread: The spread sequence generator 122takes a sequence of length n, and expresses each of spread sequences asr^((k)) when it is to generate K types (where 0<=k<K−1). The spreadsequence uses, for example, an M-sequence, etc.).

In particular the spread sequence generator 122 takes the key 104 as aninitial value and generates a spread sequence {r_(i) ⁽⁰⁾} (0<=i<n),multiplies it by a weighting value value alpha (>=1) that is determinedbeforehand, and stores the result in the real number buffer {m_(i)}(0<=1<n) Expressing this as an equation gives the following:m_(i)=alpha·r_(i) ⁽⁰⁾ (0<=i<n) (:=indicates that the value of the rightside of the equation can be substituted into the left)

Step 122) Conversion Into a Watermark Symbol Expression:

The embedding sequence generator 120 converts the watermark 103 into asymbol expression. For example, if the watermark is 4-character 8-bitsper character information and there is conversion into a symbol for eacheight bits, it is possible to convert the watermark into the watermarkfour symbols (with the value of each symbol being from 0 &tilde& 255,which is equivalent to ASCII text code). When this occurs, the number ofsymbols is smaller than K, and the maximum value a symbol can have isselected so that it is smaller than n. The value of each symbol is s_(j)(1<=j<=J(<K)), with the maximum value of s_(j) being expressed as M(<=n).

Step 123) Dispersion of the Watermark:

The embedding sequence generator 120 adds a spread sequencecorresponding to each symbol s_(j) to {m_(i)}, for each terms of j'thitem. In particular, the symbol value s_(j) is added to the key 104, thesum is used as the initial value, and the spread sequence {r_(i) ⁽⁰⁾}(0<=i<n) having the length n for the j'th item is generated by thespread sequence generator 122.

After this, the embedding sequence generator 120 adds each item of{r_(i) ^((j))} to each item {m_(i)}. Expressing this as an equationgives the following.m _(i):m _(i)+r _(i) ^((j)) (0<=i<=n)where this is repeated for the interval 1<=j<=J.

Step 124) The embedding sequence generator 120 subtract the averagevalue from each item of {m_(i)} so that the average value of {m_(i)}obtained for up to Step 123 above is 0, and outputs that result as theembedding sequence 121 which is sent to the component value changeportion 140. Expressing the subtraction processing as a formula givesthe following.

${ave}\text{:}\frac{1}{n}{\sum\limits_{i = 0}^{n - 1}m_{i}}$m_(i) = m_(i) − ave(0 ≤ i ≤ n)The following is a description of the process of the component valuechange portion 140 of the present embodiment.

The component value change portion 140 inputs the embedding objectcomponent position information 131 and the embedding sequence 121 andgenerates the watermark coefficient matrix by the procedure shown inFIG. 7.

FIG. 7 is a flow chart of the process of the component value changeportion of the first embodiment of the present invention.

Step 131) In the component value change portion 140, a watermarkcoefficient matrix F(u,v) is prepared as a complex matrix of size N×Nand the initial value is made the zero matrix.

Step 141) The component value change portion 140 uses L_(k)=(x_(k),y_(k), z_(k)) which is the embedding object component positioninformation 131 for the k'th item and changes the elements F(u,v).

Step 142) When zk is a value expressing a real number component: Thecomponent value change portion 140 adds the real number componentF(x_(k), y_(k)) to mk. In addition, so that the Fourier transformsequence holds its symmetry, the real number component of F(N−xk,N−yk)is also added to m k. Expressing this as an equation gives thefollowing:F(x _(k) ,x _(k)):=F(x _(k) ,y _(k))+m kF(N−x_(k), N−y_(k)):F(N−x_(k),N−x_(k))+m_(k)

Step 143) When zk is a value expressing an imaginary number: Thecomponent value change portion 140 adds the imaginary number componentF(xk,yk) to m k. In addition, so that the Fourier transform sequenceholds its symmetry, the real number component of F(N−x k, N−y k) issubtracted from mk. Expressing this as an equation gives the following:F(x k,y k):=F(x k,yk)+mk·iF(N−x k, N−y k):=F(N−x k,N−y k)+m k·i(where i is an imaginary number unit). The above mentioned the equationperforms in order to k=0 . . . n−1.

The following is a description of the process of the discrete Fourierinverse transform portion 150 of the first embodiment of the presentinvention.

FIG. 8 is a diagram describing the process of the discrete Fourierinverse transform portion of the first embodiment of the presentinvention.

The discrete Fourier inverse transform portion 150 obtains the watermarkpattern 151 that is the real number matrix (that has had the imaginarynumber component discarded) of size N×N obtained by performing adiscrete Fourier inverse transform on the watermark coefficient matrix141, and sends the watermark pattern 151 to the watermark pattern addingportion 110.

The following is a description of the process of the watermark patternadding portion 110 of the first embodiment of the present invention.

FIG. 9 is a diagram describing the process of the watermark patternadding portion of the first embodiment of the present invention.

The watermark pattern adding portion 110 emphasizes the watermarkpattern 151 by the value of the intensity parameter, and adds liketiling the watermark pattern 151 to the input image 101, and generatesand outputs an embedded image. Expressing this as an equation gives thefollowing.{I _(xy)}: input image (0<=x<Width, 0<=y<Height)(Width is the horizontal size of the input image, Height is the verticalsize of the input image.)

When{W _(ij)}: watermark pattern (0<=i, j<N) power: intensity parameter,it is determined byI′ _(xy):=I _(xy)+power·W _(x % N, y % N)(0<=x<Width, 0</=y<Height)(a % b) expresses the remainder when a is divided by b.) The watermarkpattern adding portion 110 outputs {I′xy} as the embedded image 105.Moreover, when the value of the intensity parameter is 1, the watermarkpattern is added without any emphasis. That is, this is the same as thecase when an intensity parameter is not used.

This ends the process of the watermark embedding apparatus 100 accordingto the present embodiment.

In the processing for the embedding of a watermark by the presentembodiment, an N×N sized 2-dimensional discrete Fourier inversetransform is used once only; With the conventional technology, it isnecessary to divide an image into blocks of N×N size discrete Fouriertransform operations and inverse discrete Fourier transform operationsfor each block. For example if there is b number of blocks, the ratio ofthe amount of embedding processing according to the first embodiment andthe conventional technology becomes 1:2b, meaning that it is possible tohave high-speed embedding processing if the first embodiment is used.

Second Embodiment

The following is a description of the processing for detecting awatermark embedded by the watermark embedding apparatus of the firstembodiment.

FIG. 10 is a diagram showing the configuration of a watermark detectionapparatus according to a second embodiment of the present invention.

A watermark detection apparatus 200 is an apparatus for detecting anembedded watermark from an image resulting from processing (partialdiscard, irreversible compression, etc.) being performed on an embeddedimage obtained using the method of the first embodiment described above.

The watermark detection apparatus 200 comprises a detected objectcomponent specification portion 210, a position marker sequencegeneration portion 220, a position marker detection portion 230, and awatermark detection portion 240.

FIG. 11 is a flow chart showing the process of a watermark detectionapparatus according to a second embodiment of the present invention.

Step 210) The watermark detection apparatus 200 inputs a key 202 whichis the same as that was used for embedding. First, in the detect objectcomponent specification portion 210, a method the same as that of theembedding object component specification portion 130 of the firstembodiment described above, is used to generate detected objectcomponent position information 211 from the key, which is sent theposition marker detection portion 230 and the watermark detectionportion 240.

Step 220) In the position marker sequence generation portion 220, aposition marker sequence 221 is generated from the key 202 and sent tothe position marker detection portion 230.

Step 230) The position marker detection portion 230 cuts an N×N (N issame as the watermark pattern size in the first embodiment) size blockfrom a detected object image 201, and, when the start point of the cutpixel block is in agreement with the start point of the embeddedwatermark pattern, the start point of the pixel block is output asoffset information 231 and sent to the watermark detection portion 240.

Step 240) The watermark detection portion 240 cuts a pixel block of sizeN×N from the offset position specified by using the detected objectimage 201, key 202, detected object component position information 211and offset information 231, detects the watermark embedded in that pixelblock and outputs a detection result 203.

The following is a description of the detected object componentspecification portion 210 in the present embodiment.

FIG. 12 is a diagram showing the configuration of the detected objectimage object component specification portion according to the secondembodiment of the present invention and FIG. 13 is a flow chart showingthe process of the detected object component specification portionaccording to the second embodiment of the present invention.

Step 211) The detected object component specification portion 210 has arandom number generator 212, inputs the key 202 and uses the randomnumber generator 212 to generate a random number sequence using said key202 as an initial value.

Step 212) The random number sequence is used as the basis for generatingthe detected object component position information 211 which is asequence having the same length as the length n of the embeddingsequence used in the previously described first embodiment.

The detected object component position information 211 has the followingconfiguration.Lk=(xk,yk,zk)(0<=k<n)

-   x k: embedding object component sequence x-direction second degree;-   y k: embedding object component sequence y-direction second degree;-   z k: flag expressing real or imaginary for the embedding object    coefficient (whether or not it is a real number component or an    imaginary number component)

The detected object component specification portion 210 has exactly thesame process as the embedding object component specification portion 130of the previously described first embodiment. That is to say, the samekey is used as the input, and the embedding object component positioninformation 131 generated by the embedding object componentspecification portion 130 of the first embodiment and the detectedobject component position information 211 generated by the detectedobject component specification portion 210 of the present embodiment areexactly the same. The generated detected object component positioninformation 211 is sent to the position marker detection portion 230.

The following is description of the position marker sequence generationportion 220 in the present embodiment.

FIG. 14 is a diagram showing the configuration of the position markersequence generation portion according to the second embodiment of thepresent invention, and FIG. 15 is a flow chart showing the process ofthe position marker sequence generation portion according to the secondembodiment of the present invention.

Step 221) The position marker sequence generation portion 220 has aspread sequence generator 222, inputs the key 202, and uses the spreadsequence generator 222 to generate a spread sequence {r_(i) ⁽⁰⁾} oflength n for the 0'th item the spread sequence having the key 202 as theinitial value and being used as it is as the position marker sequence221 ({pi} (0</=i<n) (pi:=r_(i) ⁽⁰⁾ (0<=i<n))), which is then sent to theposition marker detection portion 230. The spread sequence generator 222in the position marker sequence generation portion 220 has the sameprocess as the spread sequence generator 122 in the embedding sequencegeneration portion 120 of the previously described first embodiment.

The following is a description of the process of the position markerdetection portion 230 of the present embodiment.

FIG. 16 is a diagram showing the configuration of the position markerdetection portion according to the second embodiment of the presentinvention.

The position marker detection portion 230 shown in this figurescomprises an offset candidate information generation portion 232, ablock generation portion 233, a discrete Fourier transform portion 234,a detected object coefficient generation portion 235, a position markerdetection information generation portion 236 and an offset informationgeneration portion 237.

FIG. 17 is flow chart showing the process of the position markerdetection portion according to the second embodiment of the presentinvention.

Step 231) The position marker detection portion 230 inputs the detectedobject image 201, the detected object component position information 211and, the position marker sequence 221 and first of all, in the offsetcandidate information generation portion 232, generates offset candidateinformation 204 (a, b) from (0,0) to (N−1, N−1).

Step 232) After this, processing in the block generation portion 233 tothe position marker detection information generation portion 236 isperformed for each of the offset candidate information. FIG. 18 is adiagram describing the process of the block generation portion accordingto the second embodiment of the present invention and FIG. 19 is flowchart showing the process of the block generation portion according tothe second embodiment of the present invention. The following is adescription of the process of the block generation portion 233 withreference to FIG. 18 and FIG. 19.

Step 232-1) The block generation portion 233 inputs the detected objectimage 201 and the offset candidate information 204.

Step 232-2) A pixel block of size N×N is cut from a position offset bythe offset candidate information 204 (a, b), from the top left of thedetected object image 201.

Step 232-3) The cut pixel block is sent to the discrete Fouriertransform portion 234.

Step 233) The discrete Fourier transform portion 234 takes the pixelblock, performs a discrete Fourier transform on the pixel block togenerate a detected object coefficient matrix 206, and then sends thedetected object coefficient matrix 206 to the detected objectcoefficient generation portion 235.

Step 234) In the detected object coefficient generation portion 235, thedetected object component position information 211 and the detectedobject coefficient matrix 206 undergo the following processing toproduce a detected object coefficient. FIG. 20 is a flow chart showingthe process of the detected object coefficient generation portionaccording to the second embodiment of the present invention.

Step 234-1) If the detected object component position information 211 isexpressed as L k=(xk,yk,zk) (0<=k<n), the detected object coefficientmatrix 206 is expressed as F(u, v)(0<=u<N, 0<=v<N) and a detected objectcoefficient 207 is expressed as {qk} (0<=k<n), then the detected objectcoefficient generation portion 235 performs the following process.

Step 234-2) When z x expresses a real number component, q k=(real numbercomponent of F(x,y)).

Step 234-3) When z x expresses an imaginary number component, qk=(imaginary number component of F(x,y)).

The above processing in Steps 234-1, 234-2 is performed sequentially fork=0 . . . n−1.

Step 234-4) The detected object coefficient 207 {q k} determined by theabove processing is output.

Step 235) Next, in the position marker detection information generationportion 236, the following equation is used to determine a correlationvalue between the position marker sequence 221 and the detected objectsequence 207, pair the correlation value with the offset candidateinformation 204 and output the result as the position marker detectioninformation 208 corr ab. This position marker detection information 208is determined in accordance with the following equation.

${corr}_{ab}\text{:} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i} \cdot q_{i}} \right)}{\sqrt{\sum\limits_{i = 1}^{n - 1}p_{i}^{2}}\sqrt{\sum\limits_{i = 1}^{n - 1}q_{i}^{2}}}$

The processing in 0he above block generation portion 233 to the positionmarker detection information generation portion 236 is repeated for allof the offset candidate information (a, b) from (0,0) to (N−1, N−1).

Step 236) Of all of the input position marker detection information 208,the offset information generation portion 237 outputs that offsetcandidate information (a, b) that has the greatest correlation value forthe all of the input position marker sequences 221 and detected objectsequence 207, and sends the output offset candidate information asoffset information 231 to the watermark detection portion 240.

The offset information 231 output from the position marker detectionportion 230 indicates a degree to which the start point of the watermarkpattern was offset from the top left of the detected object image 201when it was embedded.

The following is a description of the watermark detection portion 240for the present embodiment.

FIG. 21 is a diagram showing the configuration of the watermarkdetection portion according to the second embodiment of the presentinvention. As shown in the figure, the watermark detection portion 240is configured from a block generation portion 241, a discrete Fouriertransform portion 242, a detected object sequence generation portion243, a symbol detection portion 244, and a detection result generationportion 245.

FIG. 22 is flow chart showing the process of the watermark detectionportion according to the second embodiment of the present invention.

Step 241) The watermark detection portion 240 inputs the detected objectimage 201, detected object component position information 211, theoffset information 231 and the key 202. First of all, the blockgeneration portion 241, cuts off a pixel block of size N×N pixels from aposition offset by the amount of the offset information (a, b) from thetop left of the detected object image 201.

Step 242) The discrete Fourier transform portion 242 applies a discreteFourier transform to the pixel block, generates the detected objectcoefficient matrix 247 and sends the detected object coefficient matrix247 to the detected object sequence generation portion 243.

Step 243) The detected object sequence generation portion 243 uses thesame processing as the detected object sequence generation portion 235of the position marker detection portion 230 to obtain a detected objectsequence 248 and send it to the symbol detection portion 244.

Step 244) The symbol detection portion 244 determines a correlationvalue between the key 202, and the detected object sequence 248 andgenerates symbol detection information 249.

Step 245) After all of the symbol detection information 249 has beenobtained, the detection result generation portion 245 takes a symbolcandidate value that has the largest correlation value for each of thesymbol positions in the symbol detection information 249, as a detectedsymbol.

Step 246) After detect symbols have been determined for all of thesymbol positions, the detection result generation portion 245 outputs aresult of performs an inverse transform on the detected symbols, whichresult has a watermark format, as the detection result 203.

The following is a description of the symbol detection portion 244 inthe watermark detection portion 240 described above. FIG. 23 is adiagram showing the configuration of the symbol detection portionaccording to the second embodiment of the present invention.

The symbol detection portion 244 shown in the figure is configured froma symbol candidate generation portion 2441, a symbol sequence generationportion 2442 and a symbol detection information generation portion 2443,inputs the key 202 and the detected object sequence 248, and generatesthe symbol detection information 249 for each of M symbol candidates,for each of J predetermined symbol positions for detection. Thefollowing description will be for symbol detection for the j'th item(1<=j<J).

FIG. 24 is a flow chart showing the process of the symbol detectionportion according to the second embodiment of the present invention.

Step 244-1) The symbol candidate generation portion 2441 of the symboldetection portion 244 successively generates a symbol candidate c for 0to M−1, and performs the processing from Step 2442-2 to 244-3 for eachsymbol candidate. M expresses the maximum value for the symbol value bysymbol conversion in the previously described embodiment.

Step 244-2) The following is a description of the processing performedby the symbol sequence generation portion 2442. FIG. 25 is a diagramshowing the configuration of the symbol sequence generation portionaccording to the second embodiment of the present invention, and FIG. 26is flow chart showing the process of the symbol sequence generationportion according to the second embodiment of the present invention.

Step 244-2-1) The symbol sequence generation portion 2442 inputs the key202 and the symbol candidate 2444 to a spread sequence generator 2447,and the value that is the sum of c and the key 202 is taken as theinitial value to generate a spread sequence {r_(i) ⁽⁰⁾} (0<=i<n) whichis used, as it is, as the symbol sequence 2445 {p_(i) ⁽⁰⁾} (0<=i<n)(p_(i) ⁽⁰⁾:=r_(i) ⁽⁰⁾ (0<=i<n).

Step 244-3) The symbol detection information generation portion 2443uses the detected object sequence 248, the symbol sequence 2445, thesymbol candidate 2445 and the symbol position j that is currently beingprocessed, as its input, and uses the following equation to determinethe value of a correlation between the symbol sequence 2445 and thedetected object sequence 248, and combines the correlation value, thesymbol candidate 2445 and the symbol position to generate the symboldetection information corr_(c) ^((j)) 249.

${{corr}_{c{(j)}}\text{:}} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i}^{(j)} \cdot q_{i}} \right)}{\sqrt{\sum\limits_{i = 0}^{n - 1}p_{i}^{{(j)}2}}\sqrt{\sum\limits_{i = 0}^{n - 1}q_{i}^{2}}}$

The symbol detection information 249 is sent to the detection resultgeneration portion 245.

FIG. 27 is a diagram showing the configuration of the detection resultgeneration portion according to the second embodiment of the presentinvention. The detection result generation portion 245 shown in thefigure is configured from a sequence generation portion 2451 for each ofthe symbol positions, a detected symbol generation portion 2452 and aninverse symbol transform portion 2453.

FIG. 28 is a flow chart showing the process of the detection resultgeneration portion according to the second embodiment of the presentinvention.

Step 245-1) First of all, the detection result generation portion 245inputs the symbol detection information 249 to the sequence generationportion 2451 for each of the symbol positions, divides the symboldetection information 249 for each symbol position j and generates thesequence corr _(c) ^((j)) (0<=c<M) for each symbol position and havingthe length M, for each j from j=1 &tilde& J, and sends each symbolposition sequence 2454 to the detect symbol generation portion 2452.

Step 245-2) The detected symbol generation portion 2452 inputs each ofthe sequences 2454 for each symbol position and generates a detectedsymbol s j (1<=j<J) 2455 when it finds a symbol candidate c whichproduces a maximum value for the correlation of the sequences 2454 foreach symbol position j.

Step 245-3) When each detected symbol sj has been determined, theinverse symbol transform portion 2453 transforms the detected symbol s jfrom a symbol expression to the original watermark expression (forexample, where the inverse transform corresponds to the transform in thefirst embodiment, the inverse symbol transform portion 2453 performsprocessing to treat each of the values of the four detected symbols(with the value for each of the detected symbols being from 0 &tilde&255) as ASCII codes and converts the code, into four eight-bitcharacters) and generates and outputs the detection result 203. Thisdetection result 203 indicates a watermark embedded in the detectedobject image 201.

This above processing ends the processing for the watermark detectionapparatus according to the second embodiment.

With the watermark detection according to the second embodiment asdescribed above, a block of pixels is cut from the detected object imageat the same time as the pixel block is displaced, a detected objectsequence is obtained by performing a discrete Fourier transform, and, byfinding the peak of the correlation between the detected object sequenceand the position marker sequence, the degree to which the start point ofthe watermark pattern was offset from the top left of the detectedobject image when it was embedded can be determined. By doing this, incases when the detected object image is a partial image (having a sizeof 2N×2N or more) cut from an arbitrary position of an image that hasbeen embedded with a watermark pattern by the first embodiment, it ispossible to correctly determine the position of the watermark pattern.Once the amount of offset has been determined, detecting the watermarkpattern from the pixel block starting from that position enables theembedded watermark to be correctly detected.

In addition, with the watermark detection processing according to thesecond embodiment, it is not necessary to have an original image (theinput image of the first embodiment). Thus, as has been described above,watermark detection according to the second embodiment enables withoutan original image, a watermark to be detected from an image cut from anarbitrary position of an image that has been embedded with a watermarkpattern. This has not been possible with conventional technologies.

Third Embodiment

The following is a description of use of the offset information forcyclic shift of a cut pixel block according to a third embodiment of thepresent invention.

The following description for the third embodiment is for only thoseportions that are not the same as the second embodiment.

The process of the block generation portion 233 in the position markerdetection portion 230 of the present embodiment will be described first.

FIG. 29 is a flow chart showing the process of the block generationportion according to the third embodiment of the present invention.

Step 301) The block generation portion 233 of the position markerdetection portion 230 inputs the offset candidate information 204 andthe detected object image 201.

Step 302) First of all, the block generation portion 233 cuts a block ofan N×N size from the top left of the detected object image 201 as shownin FIG. 30.

Step 303) Then, the block generation portion 233 performs cyclic shiftfor this block using the offset candidate information 204 as the basis(with portions of the block that protrude due to the paralleldisplacement being shifted to the other side of the block) and obtainsthe pixel block 205.

Expressing this pixel block as a formula gives {B ij}: for a block of anN×N size cut from the top left of the detected object image 201. Whenthe pixel block obtained by cyclic shift according to the offsetcandidate information (a, b) is expressed asB′_(ij)=B_((i+a)% N, (j+b)% N) where (0<i<n), (0<=j<N), and x % yexpresses the remainder when x is divided by y, then {B′_(ij)} is outputas the pixel block 205.

The following is a description of the process of the block generationportion 241 in the watermark detection portion 240 of the thirdembodiment of the present invention.

The block generation portion 241 in the watermark detection portion 240of the present invention inputs the detected object image 201 and theoffset information 231 and uses cyclic shift to generate the a pixelblock 246 in the same manner as the block generation portion 233 in theposition marker detection portion 230 (by the input of offsetinformation as offset candidate information), and outputs the pixelblock 246.

When the present embodiment is used for watermark detection, thenecessary size of the detected object image 201 is N×N instead of theminimum 2N×2N of the second embodiment, and so it is possible to performdetection from a smaller detected object image.

Fourth Embodiment

The following is a description of a fourth embodiment of the presentinvention in which the watermark detection depends on whether a pixelblock is cut from a detected object image having a size of N×N or more,or less than N×N.

The description will commence with the block generation portion 233 ofthe position marker detection portion 230. Portions other than thosedescribed below are the same as for the second embodiment and the thirdembodiment described above.

FIG. 31 is a diagram describing the process of the block generationportion according to the fourth embodiment of the present invention andFIG. 32 is flow chart showing the process of a block generation portionaccording to the fourth embodiment of the present invention.

Step 401) The block generation portion 233 of the position markerdetection portion 230 in the present embodiment inputs the detectedobject image 201 and the offset candidate information 204.

Step 402) The block generation portion 233 judges whether the detectedobject image 201 is N×N size or more, and shifts the processing to Step403 if it is, and to Step 404 if it is not.

Step 403) The block generation portion 233 cuts a block of size N×N fromthe top left of the detected object image.

Step 404) When the detected object image 201 is small and it is notpossible to cut a block of N×N size, the block generation portion 233cuts only a portion corresponding to the detected object image (FIG.31A), and the empty portion of the block is filled with an average valueof the pixel values of the portion corresponding to the detected objectimage and processed as that.

Step 405) The block generation portion 233 uses the block obtained bythe processing described above, performs cyclic shift in the same manneras described above for the third embodiment and obtains a pixel block.

Step 406) The block generation portion 233 outputs the obtained pixelblock 205.

The following is a description of the process of the block generationportion 241 of the watermark detection portion 240.

The block generation portion 241 of the watermark detection portion 240of the previously described third embodiment inputs the detected objectimage 201 and the offset information 231, and uses processing the sameas that for the block generation portion 233 of the position markerdetection portion 230 (inputting offset information as offset candidateinformation) to obtain and output the pixel block 246.

When there is watermark detection using the present embodiment, thenecessary size of the detected object image is an arbitrary size of N×Nor more and so it is possible to perform detection on a small objectwhen compared to the third embodiment.

Fifth Embodiment

The following is a description of a fifth embodiment of the presentinvention. Those portions not described below are the same as those ofthe previously described second embodiment.

This embodiment will describe the watermark detection portion.

FIG. 33 is a diagram showing the configuration of the watermarkdetection portion according to the fourth embodiment of the presentinvention.

The watermark detection portion 500 shown in the figure includes a blockdivision portion 510, a discrete Fourier transform portion 520, adetected object sequence generation portion 530, a symbol detectionportion 540, and a detection result generation portion 550.

FIG. 34 is flow chart showing the process of the watermark detectionportion according to the fifth embodiment of the present invention.

Step 510) The watermark detection portion 500 inputs the detected objectimage 201, the detected object component position information 211, theoffset information 231 and the key 202 and, first of all, in the blockdivision portion 510, divides the detected object image 201 into T pixelblocks of N×N size, from a position offset from the top left of thedetected object image 201 by the amount of the offset (a, b), and thengives numbers from 0 &tilde& T−1 to each of the pixel blocks obtained bydivision as shown in FIG. 35.

The following processing is performed for the t'th (0<=t<T) pixel block.

Step 520) The discrete Fourier transform portion 520 performs a discreteFourier transform on the t'th pixel block to obtain the detected objectcoefficient matrix 521.

Step 530) The detected object sequence generation portion 530 generatesa detected object sequence using the detected object component positioninformation 211 and the detected object coefficient matrix 521.

Step 540) The symbol detection portion 540 determines the correlationvalue between the detected object sequence 531 and a sequence generatedfrom the key 202 and sends symbol detection information to the detectionresult generation portion 550.

Step 550) After the symbol detection information 541 has been determinedfor each t, the detection result generation portion 550 performs symboldetection for those symbol candidate values having the largestcorrelation value, for each symbol position of the symbol detectioninformation 541.

Step 560) The detection result generation portion 550 then determinesthe detected symbols from all of the symbol positions, inverselytransforms the detect symbols into the watermark format and outputs thisas the detection result 203.

The following is a description of the symbol detection portion 540 inthe present embodiment.

FIG. 36 is a diagram showing the configuration of the symbol detectionportion according to the fifth embodiment of the present invention. Thesymbol detection portion 540 comprises a symbol candidate generationportion 541, a symbol sequence generation portion 542 and a symboldetection information generation portion 543 shown in the figure. Thesymbol detection portion 540 inputs the key 202 and the detected objectsequence 531 (obtained from the t'th pixel block) and for each symbolposition for J symbols detected beforehand, generates the symboldetection information 541 for M symbol candidates and outputs it to thedetection result generation portion 550. The following is a descriptionof j'th symbol detection (where 1<=j<J).

FIG. 37 is flow chart showing the process of the symbol detectionportion according to the fifth embodiment of the present invention.

Step 551) The symbol detection information 541 successively generatessymbol candidates c for 0 to M−1, and performs the following processingof from Step 552 through Step 553 for each of the symbol candidates. Mis the maximum symbol value obtained from a symbol transform in thepreviously described first embodiment.

Step 552) The following is a description of the symbol sequencegeneration portion 542. FIG. 38 is a diagram showing the configurationof the symbol sequence generation portion according to the fifthembodiment of the present invention, and FIG. 39 is a flow chart showingthe process of the symbol sequence generation portion according to thefifth embodiment of the present invention.

Step 552-1) The symbol sequence generation portion 542 inputs the key202 and the symbol candidate c, and the symbol sequence generationportion 542 takes a value which is the sum of c and the key 202 as theinitial value when generating the spread sequence {r_(i) ^((j))}(0<=i<n) for the length of the j'th item, and uses this as the symbolsequence 545 {p_(i) ^((j))} (0<=i<n) (p_(i) ^((j)):=r_(i) ^((j))(0<=i<n)). The symbol sequence 545 is sent to the symbol detectioninformation generation portion 543.

Step 553) The symbol detection information generation portion 543 inputsthe detected object sequence 531, the symbol sequence 545, the symbolcandidate c and the symbol position j currently being processed, usesthe following formula to determine a correlation value corr_(c)^((j)(t)) between the symbol sequence 545 and the detected objectsequence 531, and then generates the symbol detection information 4541from the correlation value, symbol candidate, symbol position and pixelblock.

${{corr}_{c}^{{(j)}{(t)}}\text{:}} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i}^{(j)} \cdot q_{i}} \right)}{\sqrt{\sum\limits_{i = 0}^{n - 1}p_{i}^{{(j)}2}}\sqrt{\sum\limits_{i = 0}^{n - 1}q_{i}^{2}}}$

The symbol detection information 541 is sent to the detection resultgeneration portion 550.

The following is a description of the detection result generationportion 550.

FIG. 40 is a diagram showing the configuration of the detection resultgeneration portion according to the fifth embodiment of the presentinvention. The detection result generation portion 550 shown in thefigure comprises a sequence generation portion 551 for each symbolposition, a detected symbol generation portion 552 and an inverse symboltransform portion 553.

FIG. 41 is a flow chart showing the process of the detection resultgeneration portion according to the fifth embodiment of the presentinvention.

Step 561) The detection result generation portion 550 inputs the symboldetect information 546 and take a detected symbol 555 as the detectionresult 203 (watermark). First, the sequence generation portion 551 foreach symbol position divides the symbol detection information 541 ofeach symbol position j, and generates a symbol position sequence 554 ofcorr_(c) ^((j)(t)) (0<=c<M, 0<t<T) for each symbol position with alength M x T, for each j from j=1 &tilde& J and sends the symbolposition sequence 554 to the detected symbol generation portion 552.

Step 562) The detected symbol generation portion 552 inputs the symbolposition sequence 554 for each symbol position j, determines a symbolcandidate c for when the value of the correlation is the greatest forthe sequence, for each symbol position, and generates a detected symbols_(j) (1<j<J).

Step 563) After all of the s j have been determined, the inverse symboltransform portion 553 performs a transform from the symbol expressioninto the original watermark expression (for example, the inversetransform, corresponding to the transform in the first embodiment, isprocessing to regard the values for the four detected symbols (with thevalue for each of the detect symbols being from 0 to 255) as individualASCII codes and convert them into four 8-bit characters), and generatesand outputs the detection result 203.

The detection result 203 indicates the watermark which is embedded inthe detected object image.

With watermark detection in the present embodiment, the detected objectimage (having a size of 2N×2N or more) is divided into blocks and thesymbol when the value of the correlation is greatest for all of theblocks is detected so that, when compared to the previously describedsecond embodiment, it is possible to perform a more accurate detection.

Sixth Embodiment

The following is description of a watermark detection portion of a sixthembodiment of the present invention. Portions other than those describedbelow are the same as those of the previously described thirdembodiment.

FIG. 42 is a diagram showing the configuration of the watermarkdetection portion according to the sixth embodiment of the presentinvention. The watermark detection portion 600 shown in the figurecomprises a block division portion 610, a discrete Fourier transformportion 620, a detected object sequence generation portion 630, a symboldetection portion 640 and a detection result generation portion 650.

FIG. 43 is a flow chart showing the process of the watermark detectionportion according to the sixth embodiment of the present invention.

Step 610) The watermark detection portion 600 inputs the detected objectimage 201, detected object component position information 211, offsetinformation 231 and key 202 and outputs the watermark as the detectionresults 203. First, the block division portion 610 divides the detectedobject image 201 from the top left into blocks of N×N size as shown inFIG. 44, and uses the offset information (a, b), in the same manner asthe block generation portion 233 of the position marker detectionportion 230, to perform cyclic offset for each block and generate Tpixel blocks of the N×N size. Furthermore, the block division portion610 gives the number 0 &tilde& T−1 to each of the pixel blocks obtainedby the division. The processing from Step 620 through Step 640 isrepeated for the t'th pixel block (0<=t<T).

Step 620) The discrete Fourier transform portion 620 performs a discreteFourier transform on the t'th pixel block 601 and obtains a detectedobject coefficient matrix 602.

Step 630) The detected object sequence generation portion 630 usesprocessing the same as that of the detected object sequence generationportion 235 of the position marker detection portion 230 to obtain adetected object sequence 663 which is sent to the symbol detectionportion 640.

Step 640) The symbol detection portion 640 determines a value of thecorrelation between the detected object sequence and a sequencegenerated from the key 202, and generates symbol detection information604. The processing from Step 620 onwards is repeated for up to the T'thitem.

Step 650) Once the symbol detection information 604 has been obtainedfor each t, the detection result generation portion 650 takes, as adetected symbol the symbol candidate value that has the correlationvalue for each of the symbol positions of the symbol detectioninformation 604.

Step 660) The detection result generation portion 650 determines thedetected symbol from all of the symbol positions and outputs, as thedetection result 203, the result of an inverse transform on the detectedsymbol into a watermark format.

The following is a description of a symbol detection portion 640 in thepresent embodiment.

FIG. 45 is a diagram showing the configuration of the symbol detectionportion according to the sixth embodiment of the present invention. Thesymbol detection portion 640 shown in the figure comprises a symbolcandidate generation portion 641, a symbol sequence generation portion643, and a symbol detection information generation portion 645.

The symbol detection portion 640 inputs the key 202 and the detectedobject sequence 663 (obtained from the t'th pixel block) and outputs thesymbol detection information 604. The symbol detection information 604is generated for the M symbol candidates 642, for each of the J symbolpositions previously set for detection, and is output to the detectionresult generation portion 650. The following is a description of thej'th symbol detection (1<j<J).

FIG. 46 is a flow chart showing the process of the symbol detectionportion according to the sixth embodiment of the present invention.

Step 641) In the symbol candidate generation portion 641, the symbolcandidate c is successively generated for 0 to M−1, and the processingfrom Step 642 to Step 643 is performed for each symbol candidate 642. Mexpresses the maximum value of the symbol value from a symbol transformin the previously described first embodiment.

Step 642) FIG. 47 is a diagram showing the configuration of the symbolsequence generation portion according to the sixth embodiment of thepresent invention. FIG. 48 is a flow chart showing the process of thesymbol sequence generation portion according to the sixth embodiment ofthe present invention.

Step 642-1) The symbol sequence generation portion 643 inputs the key202 and the symbol information c and takes the sum of the key 202 andthe symbol information c as the initial value and generates the spreadsequence {r_(i) ^((j))} (0<=i<n) and uses this as it is, as the symbolsequence 644 {p_(i) ^((j))} (0<=i<n) (p_(i) ^((j)):r_(i) ^((j))(0<=i<n)). The symbol sequence 644 is sent to the symbol detectioninformation generation portion 645.

Step 643) The symbol detection information generation portion 645 inputsthe detected object sequence 603, the symbol sequence 644, the symbolcandidate c and the symbol position j currently being processed, anduses the following formula to determine the correlation value betweenthe symbol sequence and detected object sequence, and generate thesymbol detection information corr^((j)(t)) for sets of the correlationvalue, symbol candidate, symbol position and pixel block position.

${{corr}_{c}^{{(j)}{(t)}}\text{:}} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i}^{(j)} \cdot q_{i}} \right)}{\sqrt{\sum\limits_{i = 0}^{n - 1}p_{i}^{{(j)}2}}\sqrt{\sum\limits_{i = 0}^{n - 1}q_{i}^{2}}}$

The symbol detection information 604 is sent to the detection resultgeneration portion 650.

The following is a description of the detection result generationportion 650 in the present embodiment.

FIG. 49 is a diagram showing the configuration of the detection resultgeneration portion according to the sixth embodiment of the presentinvention. The detection result generation portion 650 shown in thefigure comprises a sequence generation portion 651 for each symbolposition, a detected symbol generation portion 653, and an inversesymbol transform portion 655.

FIG. 50 is a flow chart showing the process of the detection resultgeneration portion according to a sixth embodiment of the presentinvention.

Step 651) The detection result generation portion 650 inputs the symboldetect information 604 and, first of all, in the sequence generationportion 651 for each symbol position, divides the symbol detectioninformation 604 for each symbol position j, and for j=1 &tilde& Jgenerates a symbol position sequence corr_(c) ^((i)(t)) (0<=c<M, 0<=t<T)for each symbol position of length M x T, and sends the symbol positionsequence 652 to the detected symbol generation portion 653.

Step 652) The detected symbol generation portion 653 inputs the symbolposition sequence 652 for each symbol position j, finds the symbolcandidate c for when there is the maximum correlation within thesequence for each symbol position, and generates a detected symbol s_(j)(1<=j<J). This processing is repeated until all of the s_(j) aredetermined.

Step 653) After all of the detected symbols sj have been determined, theinverse symbol transform portion 655 converts from the symbol expressioninto the watermark expression (for example, with the inverse transformcorresponding to the first embodiment having four symbols (with thevalues of the four symbols (where the value of each symbol is from 0&tilde& 255) being regarded as ASCII codes in processing for conversioninto four 8-bit characters), and the detection result 203 is generatedand output. The detection results 203 indicates the watermark embeddedin the detected object image.

With watermark detection according to the present embodiment, theminimum size of the detected object image becomes N×N and therebyenables detection from a smaller partial image than does the fifthembodiment. In addition, the number of blocks used for detection islarger than the number used by the fifth embodiment and so it ispossible to perform detection at a higher accuracy than with the fifthembodiment.

In addition, when compared to the third embodiment (which can onlydetect from one block), it is possible to perform higher accuracydetection.

Seventh Embodiment

The following is a description of a watermark detection portion of aseventh embodiment of the present invention. Those portions notdescribed below are the same as those of the previously described fourthembodiment.

FIG. 51 is a diagram showing the configuration of the watermarkdetection portion according to the seventh embodiment of the presentinvention. The watermark detection portion 700 shown in the figurecomprises a block division portion 710, a discrete Fourier transformportion 720, a detected object sequence generation portion 730, a symboldetection portion 740, and a detection result generation portion 750.

FIG. 52 is a flow chart showing the process of the watermark detectionportion according to the seventh embodiment of the present invention.

Step 710) The watermark detection portion 700 inputs the detected objectimage 201, detected object component position information 211, offsetinformation 231 and key 202, and, first of all, in the block divisionportion 710 divides the detected object image 201 from the top left intoblocks of N×N size as shown in FIG. 53, and uses the offset (a, b) inthe same manner as the block generation portion 233 of the positionmarker detection portion 230, and performs cyclic shift for each blockwhile generating T pixel blocks of the N×N size. When this is done,those blocks around the edge of the detected object image 201 that donot make up an N×N size are cut for only that portion that correspondsto the detected object image 201, and remaining portion of the N×N blockis filled with a mean value of the pixel values of the portioncorresponding to the detected object image 201. The block divisionportion 710 numbers each of the pixel blocks obtains by division, with anumber from 0 &tilde& T−1.

Step 720) The discrete Fourier transform portion 720 perform a discreteFourier transform on the t'th pixel block and obtains a detected objectcoefficient matrix 702.

Step 730) The detected object sequence generation portion 730 usesprocessing the same as that of the detected object sequence generationportion 235 of the position marker detection portion 230, to obtain adetected object sequence 703 and send it to the symbol detection portion740.

Step 740) The symbol detection portion 740 determines a correlationvalue of the detected object sequence 703 and a sequence generated fromthe key 202, and then generates symbol detection information 704.

Step 750) After the symbol detection information 704 has been obtainedfor each of the t, the detection result generation portion 750 makes thesymbol candidate value of the symbol detection information 704 with themaximum correlation value into a detected symbol, for each of the symbolpositions of the symbol detection information 704.

Step 760) After the detected symbol has been determined from each of thesymbol positions, the detection result generation portion 750 inversetransforms the detected symbol into the watermark format and outputs theresult as the detection result 203.

The following is a description of the symbol detection portion 740 inthe present embodiment.

FIG. 54 is a diagram showing the configuration of the symbol detectionportion according to the seventh embodiment of the present invention.The symbol detection portion 740 shown in the figure comprises a symbolcandidate generation portion 741, a symbol sequence generation portion743 and a symbol detection information portion 745.

The symbol detection portion 740 inputs the key 202 and the detectedobject sequence 703 (obtained from the t'th pixel block) and for each ofthe predetermined j symbol positions detected, generates the symboldetection information 704 for M symbol candidates 742 and outputs thesymbol detection information 704 to the detection result generationportion 750.

The following is a description of the j'th symbol detection (1<=j<J).

FIG. 55 is a flow chart showing the process of the symbol detectionportion according to the seventh embodiment of the present invention.

Step 741) The symbol candidate generation portion 741 successivelygenerates symbol candidates c for 0 to M−1 and performs the processingfrom Step 742 to Step 743 for each of the symbol candidates. M expressesthe maximum value of the symbol value in the previously described firstembodiment.

Step 742) The following is a description of the configuration andprocess of the symbol sequence generation portion 743. FIG. 56 is adiagram showing the configuration of the symbol sequence generationportion according to the seventh embodiment of the present invention andFIG. 57 is a flow chart showing the process of the symbol sequencegeneration portion according to the seventh embodiment of the presentinvention.

Step 742-1) The symbol sequence generation portion 743 inputs the key202 and the symbol candidate c, and takes a value which is the sum of cand the key 202 as the initial value when the spread sequence generator7431 generates a j'th spread sequence {r_(i) ^((j))} (0<=i<n) and outputit as a symbol sequence 744 {p_(i) ^((j))} (0<=i<n) (p_(i) ^((j)):=r_(i)^((j)) (0<=i<n)). The symbol sequence 744 is sent to the symboldetection information generation portion 745.

Step 743) The symbol detection information generation portion 745 inputsthe detected object sequence 703, the symbol sequence 744, the symbolcandidate c and the symbol position j currently being processed, usesthe following formula to determine the correlation value of the symbolsequence 744 and the detected object sequence 703, groups thecorrelation value, symbol candidate, symbol position and the pixel blockposition and generates the symbol detection information corr_(c)^((j)(t)).

${{corr}_{c}^{{(j)}{(t)}}\text{:}} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i}^{(j)} \cdot q_{i}} \right)}{\sqrt{\sum\limits_{i = 0}^{n - 1}p_{i}^{{(j)}2}}\sqrt{\sum\limits_{i = 0}^{n - 1}q_{i}^{2}}}$

The symbol detection information 704 is sent to the detection resultgeneration portion 750.

The following is description of the detection results generation portion750 in the present embodiment.

FIG. 58 is a diagram showing the configuration of the detection resultgeneration portion according to the seventh embodiment of the presentinvention. The detection result generation portion 750 shown in thefigure comprises the sequence generation portion 751 for each symbolposition, a detected symbol generation portion 753 and an inverse symboltransform portion 755.

FIG. 59 is a flow chart showing the process of the detection resultgeneration portion according to the seventh embodiment of the presentinvention.

Step 751) The detection result generation portion 750 inputs the symboldetection information 704, and first of all, in the sequence generationportion 751 for each symbol position, divides the symbol detectioninformation 704 into each symbol position j, generates a symbol positionsequence corr_(c) ^((j)(t)) (0=c<M, 0<=t<T) of length M×T for each ofj=1 &tilde& J, and sends the symbol position sequence 752 to thedetected symbol generation portion 753.

Step 752) The detected symbol generation portion 753 inputs the symbolposition sequence 752 for each symbol position, finds a symbol candidatec having the maximum correlation value in the sequences for each symbolposition j, and generates a detected symbol s_(j) (0</=j<J). Theprocessing of Step 751 and Step 752 is repeated until all sj aredetermined.

Step 753) After all s_(j) are determined, the inverse symbol transformportion 755 transforms the symbol expression into a watermark expression(for example, with the inverse transform corresponding to the firstembodiment having four symbols (with the values of the four symbols(where the value of each symbol is from 0 &tilde& 255) being regarded asASCII codes in processing for conversion into four 8-bit characters),and generates and outputs the detection result 203.

The detection result 203 indicates the watermark embedded in thedetected object image 201.

With the watermark detection in the present embodiment, there is nolimit relating to a minimum size of the detected object image and so itis possible to perform detection from a partial image smaller than thatof the previously described sixth embodiment. In addition, the number ofblocks used for detection is greater than for the sixth embodiment andso it is possible to perform detection at a higher accuracy whencompared to the sixth embodiment. In addition, it is also possible toperform detection at a higher accuracy when compared to the fourthembodiment (which only uses one block for detection).

Eighth Embodiment

The following is a description of the position marker detection portionthat uses offset candidate information to divide the detected objectimage into blocks and outputs an addition block which is the sum of thepixel values of the pixel blocks. Those portions not described in thefollowing are the same as those of the previously described secondembodiment.

FIG. 60 is diagram showing the configuration of a block generationportion of a position marker detection portion according to an eighthembodiment of the present invention.

The block generation portion 800 of the position marker detectionportion 230 has a block division portion 810 and a block additionportion 820.

FIG. 61 is a flow chart showing the process of the block generationportion of the position marker detection portion according to the eighthembodiment of the present invention.

Step 810) The block generation portion 800 inputs the detected objectimage 201 and the offset candidate information 204 and in the blockdivision portion 810, divides the detected object image 201 into T N×Nsized pixel blocks displaced from the top left of the detected objectimage 201 by the offset candidate information 204 (a, b) as shown inFIG. 62.

Step 820) Next, the block addition portion 820 adds all of the blocksand generates the addition block 802. When a block is expressed as aformula,B _(ij) ^((t)):=t'th block (0<=i<N, 0<=j<N, 0<=t<T),the addition block A_(ij) (0<=i<N, 0<=j<N) is obtained by

$A_{ij} = {\sum\limits_{i = 0}^{T}{B_{ij}^{(t)}\mspace{14mu}\left( {{0 \leq i < N},{0 \leq j < N}} \right)}}$

Step 830) The block generation portion 800 outputs the addition block802 to the discrete Fourier transform portion 234 as the pixel block205.

The following is a description of the block generation portion 241 ofthe watermark detection portion 240 in the present embodiment.

The block generation portion 241 of the watermark detection portion 240inputs the detected object image 201 and the offset information, and, inthe same manner as the block generation portion 233 of the positionmarker detection portion 230, (inputs the offset information as theoffset candidate information and) divides the detected object image 201into T N×N sized blocks displaced by the offset information (a, b).Then, the block generation portion 241, adds these displaced blocks andgenerates an addition block. This addition block is then output to thediscrete Fourier transform portion 242 as the pixel block 246.

The watermark detection in the present embodiment is performed bydividing the detected object image (of size 2N×2N or more) into blocksof N×N size, detecting the position marked from the block which is thesum of all blocks and detecting the watermark.

Because of the addition of the T blocks, the watermark pattern which isa repeated pattern of the N×N size is emphasized T times while thepattern of the original image has a lower correlation between blocks andso is gradually cancelled by the addition. This is to say that thedetection from the addition block reduces the influence of the originalimage and at the same time emphasizes the watermark pattern so that itis possible to perform detection at a higher accuracy than with thepreviously described second embodiment.

In addition, when compared to the second embodiment, the amount ofprocessing required for detection increases by the portion required togenerate the addition block but this amount of processing is so smallthat it can be ignored when compared to the amount of processing for theother portions of the detection processing. Furthermore, it is alsopossible to perform high-speed processing several times faster whencompared to detecting one block at a time as in the fifth embodiment.

Ninth Embodiment

The following is a description of a ninth embodiment, of the positionmarker detection portion and the watermark detection portion whichperform processing to divide the detected object image into blocks, andmake an addition block by adding the pixel values of the divided blocks,use the offset information to perform cyclic offset of this additionblock and generate a pixel block. Moreover, those portions that are notdescribed in the following are the same as those of the previouslydescribed third embodiment.

FIG. 63 is a diagram showing the configuration of the block generationportion of the position marker detection portion according to the ninthembodiment of the present invention. The block generation portion 900shown in the figure comprises a block division portion 910, a blockaddition portion 920 and a cyclic shift portion 930.

FIG. 64 is a flow chart showing the process of the block generationportion of the position marker detection portion according to the ninthembodiment of the present invention.

Step 910) The block generation portion 900 inputs the detected objectimage 201 and the offset candidate information 204 and, in the blockdivision portion 910, divides the detected object image 201 from the topleft into T blocks of N×N size, as shown in FIG. 65.

Step 920) Next, the block addition portion 920 adds all of these blocksand generates the addition block 902. When a block is expressed as aformulaB _(ij) ^((t)): t'th block (0<=i<N, 0<=j<N, 0<=t<T),the addition block A_(ij) (0<=i<N, 0<=j<N) is obtained by

$A_{ij} = {\sum\limits_{i = 0}^{T}{B_{ij}^{(t)}\mspace{14mu}\left( {{0 \leq i < N},{0 \leq j < N}} \right)}}$

The following is a description of the process of the cyclic shiftportion 930 in the block generation portion 900 of the position markerdetection portion 230 in the present embodiment.

FIG. 66 is a diagram describing the process of the cyclic shift portionof the block generation portion according to the ninth embodiment of thepresent invention.

As shown in the figure, the cyclic shift portion 930 uses the offsetcandidate information 204 as the basis for cyclic shift of the additionblock 902 and generates the pixel block 205.

The pixel block 203 is output to the discrete Fourier transform portion234. When the addition block is described

A_(ij): addition block (0<=i<N, 0<=j<N), the pixel block 246 obtained bycyclic shift using the offset candidate information (a, b) is obtainedbyC _(ij)=A _((i+a)% N, (j+b) % N) (0<=i<N, 0<=j<N)

The following is a description of the block generation portion (notshown in the figure) of the watermark detection portion 240 in thepresent embodiment.

The block generation portion 241 of the watermark detection portion 240inputs the detected object image 201 and the offset information 231 and,in the same manner as the block generation portion 900 of the positionmarker detection portion 230, (inputs the offset information as offsetcandidate information and) divides the detected object image 201 fromthe top left into T blocks of N×N pixels.

Then, an addition portion inside the block generation portion 241, addsall of these blocks and generates an addition block. Then, in a cyclicshift portion of the block generation portion 241, the offsetinformation is used as the basis for cyclic shift of the addition blockto generate the pixel block 246, which is output to the discrete Fouriertransform portion 242.

The watermark detection in the present embodiment has a necessaryminimum size of N×N pixels for the detected object image and thereforeenables detection from a detected object image much smaller than in theeighth embodiment.

Furthermore, when compared to the eighth embodiment, the number ofdivided blocks T is larger and so, when there is detection, theinfluence of the original image is lessened and the watermark pattern isemphasized so that it is possible to perform detect at a higher accuracythan with the eighth embodiment.

Also, since adding the blocks means that the influence of the originalimage is lessened when there is detection and that the watermark patternis emphasized, it is possible to perform detection at higher accuracythan with the third embodiment.

In addition, when compared to the third embodiment, the amount ofprocessing required for detect increases by the amount required togenerate the addition block, but when compared to the amount ofprocessing for portions of the detection processing, is so small that itcan be ignored. In addition, when compared to detection such as in thesixth embodiment which performs detection for one block at a time, it ispossible to perform processing that is several times faster.

Tenth Embodiment

The following is a description of a tenth embodiment of the positionmarker detection portion 230. Portions not described in the followingare the same as the previously described fourth embodiment.

In the present embodiment, the position marker detection portion 230divides the detected object image into blocks and, when it does, a blockat an edge of the detected object image may have an empty portion. Inthis case, a mean value is determined for pixel values of a portion ofthe block including the detected object image, and the empty portion ofthe block is filled with the mean value. The present embodimenttherefore differs from the ninth embodiment in this respect.

FIG. 67 is diagram showing the configuration of the block generationportion of the position marker detection portion according to the tenthembodiment of the present invention. The block generation portion 1000comprises a block division portion 1010, a block addition portion 1020and a cyclic shift portion 1030.

FIG. 68 is a flow chart showing the process of the block generationportion of the position marker detection portion of the tenth embodimentof the present invention.

Step 1010) The block generation portion 1000 inputs the detected objectimage 201 and the offset candidate information 204 and as shown in FIG.69, the block division portion 1010 divides the detected object image201 from the top left into T blocks of N×N pixels. When it does this, asshown in FIG. 70, an empty portion of a block at an edge of the detectedobject image is filled with a mean value of the pixel values of theportion of the block including the detected object image 201.

Step 1020) Then, in the block addition portion 1020, all of these blocksare added and an addition block 1012 is generated. Expressing a block asa formula givesB _(ij) ^((t)): t'th block (0<=i<N, 0<=j<N, 0<=t<T)and the addition block A_(ij) (0<=i<N, 0<=j<N) is obtained by

$A_{ij} = {\sum\limits_{i = 0}^{T}{B_{ij}^{(t)}\mspace{14mu}\left( {{0 \leq i < N},{0 < j < N}} \right)}}$

The following is a description of the process of the cyclic shiftportion 1030 in the block generation portion 1000 of the position markerdetection portion 230 in the present embodiment.

FIG. 71 is a diagram showing the process of the cyclic shift portionaccording to the tenth embodiment of the present invention.

The cyclic shift portion 1030 uses the offset candidate information 204as the basis for cyclic shift of the addition block 1012 and generatesthe pixel block 205. The pixel block 205 is output to the discreteFourier transform portion 234. Expressing the addition block 1012 as aformula gives

A_(ij): addition block (0<=i<N, 0<=j<N) and the pixel block 205 obtainedby cyclic shift using the offset candidate information (a, b) isobtained byC _(ij)=A _((i+a) % N, (j+b) % N) (0<=i<N, 0<=j<N)

The following is a description of the block generation portion (notshown in the figure) of the watermark detection portion in the tenthembodiment of the present invention.

The block generation portion of the watermark detection portion in thetenth embodiment of the present invention inputs the detected objectimage and the offset information, and in the same manner as the blockgeneration portion of the position marker detection portion, (inputs theoffset information as the offset candidate information and), divides thedetected object image from the top left into T blocks of N×N pixels.

Then, a block addition portion, adds all of the blocks to generate anaddition block. Then, a cyclic shift portion uses the offset informationas the basis for cyclic shift of the addition block and generates thepixel block 246 which is then output to the discrete Fourier transformportion 242.

Watermark detection in the present embodiment has an arbitrary size fora minimum necessary size of the detected object image and enablesdetection from a detected object image smaller than that for the ninthembodiment.

Futhermore, the number of divided blocks T is smaller than for the ninthembodiment and so the influence of the original image is lessened whenthere is detection, and the watermark pattern is more emphasized, sothat it is possible to perform detection at a higher accuracy than forthe ninth embodiment.

In addition, since the addition of the blocks reduces the influence ofthe original image when there is detection and emphasizes the watermarkpattern, it is possible to perform detection at a higher accuracy thanfor the fourth embodiment.

In addition, when compared to the fourth embodiment, the amount ofprocessing required for the watermark detection increases by the amountneeded to generate the addition block, but when compared to the amountof processing for other portions of the detection processing, it issmall enough to be ignored. Furthermore, it is also possible to performprocessing that is faster in proportion to the number of blocks, whencompared to the seventh embodiment that performs detection for one blockat a time.

Eleventh Embodiment

The following is a description of a watermark detection apparatusaccording to an eleventh embodiment of the present invention.

The watermark detection apparatus according to the present embodiment isan apparatus for detecting an embedded watermark from an image resultingfrom processing (such as partial cutting, irreversible compression orthe like) being applied to an embedding obtained using the method of thefirst embodiment, described above.

FIG. 72 is a diagram showing the configuration of the watermarkdetection apparatus according to the eleventh embodiment of the presentinvention. The watermark detection apparatus 1100 shown in the figurecomprises a position marker detection portion 1110, a position markersequence generating portion 1120, a detected object componentspecification portion 1130 and a watermark detection portion 1140.

FIG. 73 is a diagram showing the configuration of the watermarkdetection apparatus according to the eleventh embodiment of the presentinvention.

Step 1110) The watermark detection apparatus 1100 inputs the detectedobject image 201 and the key 202 used when there was embedding. First,in the detected object component specification portion 1130 of theinformation detection apparatus 1100, a method the same as that used bythe embedding object component specification portion 130 in thepreviously described first embodiment is used to generate detectedobject component position information 1103 from the key 202, and thensend this detected object component position information 1103 to theposition marker detection portion 1110 and the watermark detectionportion 1140.

Step 1120) The position marker sequence generating portion 1120generates a position marker sequence 1102 from the key 202 and sends theposition marker sequence 1102 to the position marker detection portion1110.

Step 1130) The position marker detection portion 1110 cuts pixel blocksof N×N size (where N is the size of the embedded watermark pattern inthe first embodiment) from the top left of the detected object image 201and outputs offset information 1101 which indicates the degree to whichthe start point of the embedded watermark pattern is displaced from thestart point of the cut pixel block, and sends it to the watermarkdetection portion 1140.

Step 1140) The watermark detection portion 1140 inputs the detectedobject image 201, the key 202, the detected object component positioninformation 1103 and the offset information 1101, cuts N×N size pixelblocks from the top left of the detected object image 201, and uses theoffset information 1101, the key 202 and the detected object componentposition information 1103 to detect the watermark embedded in the pixelblock and output the detection result 203.

The following is a description of the detected object componentspecification portion 1130 in the present embodiment.

FIG. 74 is a diagram showing the configuration of the detected objectcomponent specification portion according to the eleventh embodiment ofthe present invention, and FIG. 75 is a flow chart showing the processof the detected object component specification portion according to theeleventh embodiment of the present invention.

Step 1111) The detected object component specification portion 1130inputs the key 202 and uses a random number generator 1131 to generate arandom number sequence that has the key 202 as an initial value.

Step 1112) Furthermore, the detected object component specificationportion 1130 uses the generated random number sequence as the basis forgenerating the detected object component position information 1103 whichis a sequence having the same length as the length n of the embeddingsequence used in the first embodiment. The detected object componentposition information 1103 is configured as follows.Lk=(xk,yk,zk) (0<=k<n)

-   xk: embedding object component coefficient x-direction second    degree;-   yk: embedding object component coefficient y-direction second    degree;-   zk: flag expressing real or imaginary for the embedding object    coefficient (where or not it is a real number component or an    imaginary number component)

The detected object component specification portion 1130 performsexactly the same process as the embedding object component specificationportion in the first embodiment. That is to say, it inputs the same key,and the embedding object component position information generated by theembedding object component specification portion of the first embodimentis exactly the same as the detected object component positioninformation 1103 generated by the detected object componentspecification portion 1130 of the present embodiment. The generateddetected object component position information 1103 is sent to theposition marker detection portion 1110.

The following is a description of the position marker sequencegenerating portion 1120 in the present embodiment.

FIG. 76 is diagram showing the configuration of the position markersequence generating portion according to the eleventh embodiment of thepresent invention and FIG. 77 is a flow chart showing the process of theposition marker sequence generating portion according to the eleventhembodiment of the present invention.

Step 1121) The position marker sequence generating portion 1120 inputsthe key 202 and uses a spread sequence generator 1121 to generate aspread sequence {r_(i) ⁽⁰⁾} (0<=i<n) of 0'th length n and having the key202 as its initial value, and uses this spread sequence as it is as theposition marker sequence {p_(i)} (0<=i<n) (p_(i):=r i⁽⁰⁾ (0<=i<n)). Thespread sequence generator 1121 of the position marker sequencegenerating portion 1120 uses an process the same as the spread sequencegenerator 122 of the position marker sequence generating portion 120 ofthe first embodiment.

The following is a description of the position marker detection portionof the present embodiment.

FIG. 78 is a diagram showing the configuration of the position markerdetection portion of the eleventh embodiment of the present invention.

The position marker detection portion 1110 shown in the figure comprisesa block generating portion 1111, a discrete Fourier transform portion1113, a detected object sequence generating portion 1115, an offsetcandidate information generating portion 1117, a position markerdetection information generating portion 1118, and an offset informationgenerating portion 1119.

FIG. 79 is a flow chart showing the process of the position markerdetection portion of the eleventh embodiment of the present invention.

Step 1131) The position marker detection portion 1110 inputs thedetected object image 201, the detected object component positioninformation 1103, and the position marker sequence 1102 and first ofall, in the block generating portion 1111, cuts pixel blocks of N×N sizefrom the top left of the detected object image 201.

Step 1132) Next, the discrete Fourier transform portion 1113 performs adiscrete Fourier transform on the pixel block 1104 and generates adetected object coefficient matrix 1105.

Step 1133) Next, the offset candidate information generating portion1117 successively generates offset candidate information (a, b) for (0,0) to (N−1, N−1).

Step 1134) Next, the processing for the detected object sequencegenerating portion 1115 to the position marker detection informationgenerating portion 1118 is performed for each of the offset candidateinformation 1106. The detected object sequence generating portion 1115inputs the detected object component position information 1103, thedetected object coefficient matrix 1105 and the offset candidateinformation 1106 and generates a detected object sequence 1107 asfollows. FIG. 80 is a flow chart showing the process of the detectedobject sequence generating portion of the position marker detectionportion of the eleventh embodiment of the present invention.

Step 1134-1) The detected object sequence generating portion 1115expresses the detected object coefficient matrix 1105 as F(u, v)(0<=u<N, 0<=v<N), the detected object component position information1103 as L k=(xk,yk,zk) (0<=k<n), the offset candidate information 1106as (a, b) and the detected object sequence 1107 as {q k} (0<=k<n).

When zk is a value that expresses a real number component, there is ashift to Step 1134-2 and when z k is a value that express an imaginarynumber component, there is a shift to Step 1134-3.

Step 1134-2) Processing for the real number component of

${q_{k}\text{:}} = {{F\left( {x_{k},y_{k}} \right)} \times {\mathbb{e}}^{\frac{{{a \cdot x}\; 1} + {b \cdot {yk}}}{N}}}$is performed for k=0 &tilde& n−1

Step 1134-3) Processing for the imaginary number component of

${q_{k}\text{:}} = {{F\left( {x_{k},y_{k}} \right)} \times {\mathbb{e}}^{\frac{{{a \cdot x}\; 1} + {b \cdot {yk}}}{N}}}$is performed for k=0 &tilde& n−1.

Step 1134-4) The detected object sequence {qk} is output.

Step 1135) Next, the position marker detection information generatingportion 1118 uses the following formula to determine the value of thecorrelation between the position marker sequence 1102 and the detectedobject sequence 1107, group it with the offset candidate information1106 and output it as the position marker detection informationcorr_(ab).

${{corr}_{ab}\text{:}} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i} \cdot q_{i}} \right)}{\sum\limits_{i = 0}^{n - 1}\;{p_{i}^{2}{\sum\limits_{i = 0}^{n - 1}\; q_{i}^{2}}}}$

The processing from the detected object sequence generating portion 1115and the position marker detection information generating portion 1118 isrepeated until the offset candidate information (a, b) has passed from(0,0) &tilde& (N−1, N−1), and all of the position marker detectioninformation 1108 is sent to the offset information generating portion1119.

Step 1136) The offset information generating portion 1119 takes theoffset candidate information (a, b) for that item of input positionmarker detection information 1108 for which the value of the correlationbetween the position marker sequence 1102 and the detected objectsequence 1109 is greatest, outputs it as the offset information 1101 andsends it to the watermark detection portion 1140.

The offset information 1101 output from the position marker detectionportion 1110 indicates the degree to which the start point of thewatermark pattern was offset from the top left of the detected objectimage 201 when it was embedded.

The following is a description of the watermark detection portion 1140in the present embodiment.

FIG. 81 is a diagram showing the configuration of the watermarkdetection portion according to the eleventh embodiment of the invention.The watermark detection portion 1140 in the figure comprises a blockgenerating portion 1141, a discrete Fourier transform portion 1143, adetected object sequence generating portion 1145, a symbol detectionportion 1147 and a detection result generating portion 1149.

FIG. 82 is a flow chart showing the process of the watermark detectionportion according to the eleventh embodiment of the present invention.

Step 1141) The block generating portion 1141 inputs the detected objectimage 201, detected object component position information 1103, offsetinformation 1101 and key 202 and, first of all, in the block generatingportion 1141, cuts pixel blocks 1142 of a size N×N from the top left ofthe detected object image 201, and sends the pixel blocks 1142 to thediscrete Fourier transform portion 1143.

Step 1142) The discrete Fourier transform portion 1143 performs adiscrete Fourier transform on the pixel blocks 1142 and generates aredetected object coefficient matrix 1144 which is then sent to thedetected object sequence generating portion 1145.

Step 1143) The detected object sequence generating portion 1145 obtainsa detected object sequence 1146 (using the offset information 1101 asthe offset candidate information) by a processing the same as that ofthe detected object sequence generating portion 1115 of the positionmarker detection portion 1110, and sends the detected object sequence1146 to the symbol detection portion 1147.

Step 1144) The symbol detection portion 1147 determines the value of thecorrelation between the detected object sequence 1146 and a sequencegenerated from the key 202, and generates symbol detection information1148.

Step 1145) The detection result generating portion 1149 obtains thesymbol detection information 1148 and then, for each of symbol positionsof the symbol detection information 1148, selects, as a detected symbol,a symbol candidate value having a maximum value of the correlation.

Step 1146) After all of the detected symbols have been determined fromall of the symbol positions, a result of performing an inverse transformon the detected symbol to produce a watermark is output as the detectionresult 203.

The following is a description of the symbol detection portion 1147 inthe present embodiment.

FIG. 83 is diagram showing the configuration of the symbol detectionportion according to the eleventh embodiment of the present invention.In the figure, the symbol detection portion 1147 comprises a symbolcandidate generating portion 11471, a symbol sequence generating portion11473 and a symbol detection information generating portion 11475. Thesymbol detection portion 1147 inputs the key 202 and the detected objectsequence 1146 and for each of predetermined J symbol positions detected,generates the symbol detection information 1148 for M symbol candidates,and outputs the symbol detection information 1148 to the detectionresult generating portion 1149. The following is a description of thej'th (1<=j<J) symbol detection.

FIG. 84 is a flow chart showing the process of the symbol detectionportion according to the eleventh embodiment of the present invention.

Step 1144-1) The symbol candidate generating portion 11471 successivelygenerates symbol candidates c from 0 to M−1, and the processing fromStep 1144-2 &tilde& Step 1144-3 is performed for each symbol candidate.M expresses the maximum value of the symbol value due to symbolconversion in the previously described first embodiment.

Step 1144-2) The following is a description of the symbol sequencegenerating portion 11473.

FIG. 85 is diagram showing the configuration of the symbol sequencegenerating portion according to the eleventh embodiment of the presentinvention and FIG. 86 is a flow chart showing the process of the symbolsequence generating portion according to the eleventh embodiment of thepresent invention.

Step 1144-2-1) The symbol sequence generating portion 11473 inputs thekey 202 and the symbol candidate c, and takes a value which is the sumof c and the key 202 as an initial value for a spread sequence generator114731 generating the j'th spread sequence {r_(i) ^((j))} of length n,which is used as it is as a symbol sequence 11474 {p_(i) ^((j))}(0<=i<n) (p_(i) ^((j))>:=r_(i) ^((j)) (0<=i<n)). The symbol sequence11474 is sent to the symbol detection information generating portion11475.

Step 1144-3) The symbol detection information generating portion 11475inputs the detected object sequence 1146, the symbol sequence 11474, thesymbol candidate c and the symbol position j that is currently beingprocessed and uses the following formula to determined the value of thecorrelation between the symbol sequence 11474 and the detected objectsequence 1146. The correlation value, the symbol candidate and thesymbol position are then grouped and the symbol detection informationcorr_(c) ^((j)) generated.

${{corr}\text{:}} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i}^{(j)} \cdot q_{i}} \right)}{\sum\limits_{i = 0}^{n - 1}q_{i}^{2}}$

The symbol detection information 1148 is sent to the detection resultgenerating portion 1149.

The following is a description of the detection result generatingportion 1149.

FIG. 87 is diagram showing the configuration of the detection resultgenerating portion according to the eleventh embodiment of the presentinvention. The detection result generating portion 1149 shown in thefigure comprises a sequence generating portion 11491 for each of thesymbol positions, a detected symbol generating portion 11493 and aninverse symbol transform portion 11495.

FIG. 88 is a flow chart showing the process of the detection resultgenerating portion according to the eleventh embodiment of the presentinvention.

Step 1145-1) The detection result generating portion 1149 inputs thesymbol detection information 1148 and first of all, in the sequencegenerating portions 11491 for each of the symbol positions, divides thesymbol detection information 1148 for each symbol position j, andgenerates a symbol position sequence corr_(c) ^((j)), (0<=c<M) of lengthM for each of the symbol positions for j=1 &tilde& J, and sends thesymbol position sequence 11492 to the detected symbol generating portion11493.

Step 1145-2) The detection symbol generating portion 11493 inputs thesymbol position sequence 11492 for each of the symbol positions andfinds the symbol candidate c in the sequence for each symbol position j,for which the value of the correlation is maximum, and generates adetected symbol s_(j) (1</=j<J).

Step 1145-3) After all of the sj have been determined, the inversesymbol transform portion 11495 transforms from symbol expression intothe original watermark expression (with, for example, the inversetransform corresponding to the transform in the first embodiment havingfour symbols (where the value of each symbol is from 0 &tilde& 255)being regarded as ASCII code in processing for conversion into four8-bit characters), and generates and outputs the detection result 203.

The detection result indicates the watermark embedded in the detectedobject image 201.

This ends the processing for the watermark detection apparatus in theeleventh embodiment.

Watermark detection in the present embodiment involves cutting a blockfrom the top left of the detected object image, performing a discreteFourier transform and obtaining the detected object coefficient matrix1105, and then multiplying a phase difference determined by the seconddegree of the coefficient and the offset, with the component specifiedby the detected object component position information 1103, andgenerating the detected object sequence. The aspect relating to theparallel displacement of the Fourier transform uses

$\left. {F\left( {u,v} \right)}^{{- 2}\;\pi\; i\frac{{a \cdot u} + {b \cdot u}}{N}}\leftarrow\left. \rightarrow{f\left( {{x - a},{y - b}} \right)} \right. \right.$(with <--> expressing a Fourier transform/inverse transform). By this,the discrete Fourier transform necessary when there is detection is onlyapplied once, and it is possible to perform processing that is fasterthan the detection processing of the first through the tenthembodiments. Using a computer simulation for a comparison of theprocessing times for a block size of N=128 gave a second embodiment toeleventh embodiment ratio of 65:1.

In addition, it is possible to perform detection when there is a partialimage (of size N×N or more) cut from an arbitrary position of anembedded image embedded with a watermark according to the firstembodiment.

Twelfth Embodiment

The following is a description of a twelfth embodiment, using an exampleof a block generating portion in the position marker detection portion.In this embodiment, the block generating portion, when the detectedobject image is divided into blocks, determines an average value of aportion of a block including the detected object image, and a remainingempty portion of the block is filed with the average value. In thefollowing description, those portions that are not described are thesame as the previously described eleventh embodiment.

FIG. 89 is a diagram describing the process of the block generatingportion of the position marker detection portion according to thetwelfth embodiment of the present invention.

The block generating portion 1111 of the position marker detectionportion 1110 inputs the detected object image 201 and cuts blocks of N×Nsize from the top left of the detected object image. If the detectedobject image is smaller than the N×N size, a portion of a blockcontaining the detected object image is cut (see A in the figure), andthe remaining empty portion is filled with a mean value of the pixelvalue of the portion containing the detected object image.

A block obtained by this processing is output as a pixel block in thesame manner as the previously described eleventh embodiment.

The following is a description of the block generation process of thewatermark detection portion in the present embodiment. The blockgeneration process of the watermark detection portion in the presentembodiment inputs the detected object image, and uses a processing thesame as that of the block generating portion in the position markerdetection portion to obtain and output a pixel block.

When compared to the previously described eleventh embodiment, watermarkdetection using the present embodiment uses an arbitrary size from thenecessary size of N×N or more and therefore enables detection from asmaller detected object image.

Thirteenth Embodiment

The following is a description of a thirteenth embodiment of the presentinvention, for the watermark detection portion, the symbol detectionportion and the detection result generating portion. Those portions notdescribed in the following are the same as those of the previouslydescribed eleventh embodiment.

FIG. 90 is a diagram showing the configuration of the watermarkdetection portion according to the thirteenth embodiment of the presentinvention. The watermark detection portion 2000 shown in the figurecomprises a block division portion 2100, a discrete Fourier transformportion 2200, a detected object sequence generating portion 2300, asymbol detection portion 2400, and a detection results generatingportion 2500.

FIG. 91 is a flow chart showing the process of the watermark detectionportion according to the thirteenth embodiment of the present invention.

Step 2100) The watermark detection portion 2000 inputs the detectedobject image 201, the detected object component position information211, the offset information 231 and the key 202 and first of all, in theblock division portion 2100 divides the detected object image 201 fromthe top left into T pixel blocks 2001 of N×N size as shown in FIG. 92.

Step 2200) The pixel blocks 2001 obtained by division are given numbersfrom 0 &tilde& T−1. The processing of Step 2300 &tilde& Step 2400 isrepeated for the t'th pixel block (0<=t<T).

Step 2300) The discrete Fourier transform portion 2200 performs adiscrete Fourier transform on the t'th pixel block to obtain a detectedobject coefficient matrix 2002.

Step 2400) The detected object sequence generating portion 2300 performsa processing the same as that of the detected object sequence generatingportion of the position marker detection portion to obtain a detectedobject sequence 2003 which is then sent to the symbol detection portion2400.

Step 2500) The symbol detection portion 2400 determines the value of thecorrelation between the detected object sequence 2003 and a sequencegenerated from the key 202, and generates symbol detection information2004.

Step 2600) The detection result generating portion 2500 obtains thesymbol detection information 2004 for each t, and then for each symbolposition of the symbol detection information 2004, selects a detectedsymbol having a maximum value of the correlation from all of the symbolpositions, and outputs a result of performing an inverse transform onthe detected symbol to produce a digital watermark, as a detectionresult.

The following is a description of the symbol detection portion 2400 inthe present embodiment.

FIG. 93 is diagram showing the configuration of the symbol detectionportion according to the thirteenth embodiment of the present invention.The symbol detection portion 2400 in the figures comprises a symbolcandidate generating portion 2410, a symbol sequence generating portion2420 and a symbol detection information generating portion 2430.

The symbol detection portion 2400 inputs the key 202 and the detectedobject sequence 2003 (obtained from the t'th pixel block) and generatessymbol detection information 2004 for M symbol candidates for eachsymbol positions for a predetermined number J of detected symbols, andoutputs the symbol detection information 2004 to the detection resultgenerating portion 2500.

FIG. 94 is a flow chart showing the process of the a symbol detectionportion of the thirteenth embodiment of the present invention.

Step 2410) The symbol candidate generating portion 2410 successivelygenerates symbol candidates c from 0 &tilde& M−1 and repeats theprocessing of Step 2420 &tilde& Step 2430 for each symbol candidate. Mexpresses the maximum value for the symbol value due to symbol transformin the first embodiment.

Step 2420) The following is a description of the symbol sequencegenerating portion 2420. FIG. 95 is a diagram showing the configurationof the symbol sequence generating portion according to the thirteenthembodiment of the present invention, and FIG. 96 is a flow chart showingthe process of the symbol sequence generating portion according to thethirteenth embodiment of the present invention.

Step 2421) The symbol sequence generating portion 2420 inputs the key202 and the symbol candidate c, and uses the sum of the key 202 and thesymbol candidate c as an initial value for a spread sequence generator2421 generating the j'th spread sequence {r_(i) ^((j))} of length n, andusing it as it is as the symbol sequence 2402.{p _(i) ^((j))} {0<=i<n) (p _(i) ^((j)):=r _(i) ^((j)) (0<=i<N))The symbol sequence 2402 is sent to the symbol detection informationgenerating portion 2430.

Step 2430) The symbol detection information generating portion 2430inputs the detected object sequence 2003, the symbol sequence symbol2402, the symbol candidate c and uses the symbol position j that iscurrently being processed, and the following formula to determine thevalue of the correlation between the symbol sequence 2402 and thedetected object sequence 2003, group the correlation value, the symbolcandidates, symbol position j and the pixel block position and generatethe symbol detection information corr_(c) ^((j)(t)).

${{corr}_{c}^{{(j)}{(t)}}\text{:}} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i}^{(j)} \cdot q_{i}} \right)}{\sqrt{\sum\limits_{i = 0}^{n - 1}p_{i}^{{(j)}2}}\sqrt{\sum\limits_{i = 0}^{n - 1}\; q_{i}^{2}}}$

The symbol detection information 2004 is sent to the detection resultgenerating portion 2500.

The following is a description of the detection result generatingportion 2500 in the present embodiment.

FIG. 97 is diagram showing the configuration of the detection resultgenerating portion according to the thirteenth embodiment of the presentinvention. The detection result generating portion 2500 in thethirteenth embodiment of the present invention comprises a sequencegenerating portion 2510 for each of the symbol positions j, a detectedsymbol generating portion 2520 and an inverse symbol transform portion2530.

FIG. 98 is a flow chart showing the process of the detection resultgenerating portion according to the thirteenth embodiment of the presentinvention.

Step 2510) The detection result generating portion 2500 inputs thesymbol detection information 2004 and first of all, in the sequencegenerating portion 2510 for each of the symbol positions, divides thesymbol detection information 2004 into each symbol position j, andgenerates a symbol position sequencecorr_(c) ^((i)(j)) (0<=c<M, 0<=t<T)of length M×T for each symbol position, for each j from j=1 &tilde& J,and sends the symbol position sequence 2501 to the detected symbolgenerating portion 2520.

Step 2520) The detected symbol generating portion 2520 inputs eachsymbol position sequence 2501, determines the symbol candidate c havingthe maximum correlation value in each sequence for each symbol positionj, and generates a detected symbol s j (0<=j<J). This processing isrepeated until all of the s_(j) are determined.

Step 2530) Once all of the s j have been determined, the inverse symboltransform portion 2530 transforms the symbol expression into an originalwatermark expression, and generates and outputs a detection result. Forexample, the inverse transform corresponds to the transform in the firstembodiment having four symbols with the values of the four symbols(where the value of each symbol is from 0 &tilde& 255) being regarded asASCII codes in processing for conversion into four 8-bit characters.

The detection result indicates the watermark embedded in the detectedobject image 201.

Information detection in the present embodiment divides the detectedobject image 201 into blocks (of size N×N of more), and detects thesymbol for which the correlation is maximum in all the blocks so that itis possible to perform detection at a higher accuracy when compared tothe previously described eleventh embodiment. Furthermore, the number ofdiscrete Fourier transforms necessary for detection processing is thesame as the number of blocks and so it is possible to perform fasterprocessing than in the fifth embodiment.

Fourteenth Embodiment

The following is a description of processing when a block of N×N sizecannot be cut from the detected object image 201 in the block divisionportion of the watermark detection portion of a fourteenth embodiment ofthe present invention.

FIG. 99 is a diagram describing the process of the block divisionportion of the watermark detection portion according to the fourteenthembodiment of the present invention.

The block division portion 2100 divides the detected object image 201from the top left into blocks of N×N size. When it does this, a block ofan edge of the detected object image 201 may have an empty portion. Inthis case, a mean value is determined for the pixel values of theportion of the block including the detected object image, an the emptyportion of the block is filled with that mean value and processed.Numbers from 0 &tilde& T−1 are given to the pixel blocks obtained by thedivision.

Information detection according to the present embodiment is improvedbecause of the arbitrary size used as the necessary minimum size of thedetected object image, and enables detection from a detected objectimage that is much smaller than that of the previously describedthirteenth embodiment.

Furthermore, the number of discrete Fourier transforms necessary fordetection processing is the same as that of the number of blocks and soit is possible to have faster processing than in the sixth embodiment.

Fifteenth Embodiment

The following is a description of the position marker detection portionand the watermark detection portion of the fifteenth embodiment of thepresent invention.

FIG. 100 is a diagram showing the configuration of the block generatingportion of the position marker detection portion according to afifteenth embodiment of the present invention. The block generatingportion 3000 shown in the figure comprises a block division portion 3100and a block addition portion 3200.

FIG. 101 is a flow chart showing the process of the block generatingportion of the position marker detection portion according to thefifteenth embodiment of the present invention.

Step 3100) The block generating portion 3000 inputs the detected objectimage 201 and as shown in FIG. 102, the block division portion 3100divides the detected object image 201 into T blocks of N×N pixels, fromthe top left.

Step 3200) Next, the block addition portion 3200 adds all of theseblocks and generates an addition block 3002. Expressing this as aformula gives the following. When B_(ij) ^((t)): t'th block (0<=i<N,0<=j<N, 0<=t<T), the addition block A_(ij) (0<=i<N, 0<=j<N) is obtainedfrom

$A_{ij} = {\sum\limits_{i = 0}^{T}{B_{ij}^{(t)}\mspace{14mu}\left( {{0 \leq i < N},{0 \leq j < N}} \right)}}$

This addition block 3002 is output to the discrete Fourier transformportion as the pixel block 205.

Information detection with the present embodiment divides the detectedobject image 201 (of a size of N×N or more) into blocks of N×N size andperforms detection of the position marker and detection of the watermarkfrom blocks which are the sum of all of the blocks.

The adding of T blocks means that the watermark pattern which is arepeated pattern of size N×N is emphasized T times, and that theoriginal image pattern has a lower correlation between blocks, and isgradually cancelled by addition. This is to say that detection from theaddition block lessens the influence of the original image and at thesame time emphasizes the watermark pattern so that it is possible toperform detection at a higher accuracy than the eleventh embodiment.

In addition, when compared to the eleventh embodiment, the amount ofprocessing for detection increases by the amount required for generatingthe added block, but when compared to the amount of processing for otherportions of detection processing, this amount of processing is so smallas to be able to be ignored. In addition, when compared to thethirteenth embodiment that performs detection of one block at a time, itis possible to perform processing that is faster in proportion to thenumber of blocks.

Furthermore, only one discrete Fourier transform is necessary when thereis detection processing and so it is possible to have faster processingthan any of embodiments two through ten.

Sixteenth Embodiment

The following is a description of a sixteenth embodiment of the presentinvention, for the position marker detection portion and the blockgenerating portion. Those portions not described in the following arethe same as those of the twelfth embodiment.

FIG. 103 is a diagram showing the configuration of the block generatingportion of the position marker detection portion according to thesixteenth embodiment of the present invention. The block generatingportion 4000 in the figure comprises the block division portion 4100,and a block addition portion 4200.

FIG. 104 is flow chart showing the process of the block generatingportion of the position marker detection portion according to thesixteenth embodiment of the present invention.

Step 4100) The block generating portion 4000 inputs the detected objectimage 201 and as shown in FIG. 105 divides the detected object image 201from the top left into T blocks of N×N pixels. When it does this, ablock at an edge of the detected object image 201 may have an emptyportion. In this case a mean value is determined for the pixel value ofthe portion of the block including the detected object image 201 and theempty portion filled with this mean value.

Step 4200) After this, the block addition portion 4200 adds all of theblocks and generates an addition block 4001. Expressing this as aformula gives the following. WhenB _(ij) ^((t)): t'th block (0<=i<N, 0<=j<N, 0<=t<T),the addition block A_(ij) (0<=i<N, 0<=j<N) is obtained from

$A_{ij} = {\sum\limits_{i = 0}^{T}{B_{ij}^{(t)}\mspace{14mu}\left( {{0 \leq i < N},{0 \leq j < N}} \right)}}$

Step 4300) This addition block is output to the discrete Fouriertransform portion as the pixel block.

The following is a description of the block generating portion in thewatermark detection portion of the present embodiment.

The watermark detection portion of the present embodiment inputs thedetected object image 201 and in the same manner as the block generatingportion 4000 of the position marker detection portion, divides thedetected object image from the top left into T blocks of N×N pixels.

After this, in the block addition portion all of these blocks are addedto generate an addition block. This addition block is output to thediscrete Fourier transform portion as a pixel block.

Information detection in the present embodiment described above uses anarbitrary size as the necessary minimum size of the detected objectimage and, when compared to the previously described fifteenthembodiment, enables detection from a smaller detected object image.

Furthermore, when compared to the fifteenth embodiment, the number T ofdivided blocks is larger and so the influence of the original image islessened in detection, and the watermark pattern is more emphasized, andso it is possible to perform detection at a higher accuracy than withthe fifteenth embodiment.

In addition, adding the blocks lessens the influence of the originalimage when there is detection, and also emphasizes the watermarkpattern, so that it is possible to perform pattern detection at a higheraccuracy than with the twelfth embodiment.

In addition, when compared to the twelfth embodiment, the amount ofprocessing for detection increases by the portion required forgenerating the addition block, but when compared to the amount ofprocessing for other portions of detection processing, is small enoughto be ignored. Also, it is possible to perform detection at a higheraccuracy when compared to detection in the case such as with thefourteenth embodiment where detection is performed one block at a time.

Seventeenth Embodiment

The following is a description of a seventeenth embodiment of thepresent invention, for the detected object sequence generating portionof the position marker detection portion. Those portions not describedin the following are the same as the sixteenth embodiment.

In the present embodiment, the detected object sequence generatingportion of the position marker detection portion of each of theembodiments two through sixteen has as the final stage the generation ofthe detected object sequence as disclosed for each of the embodiments,but then performs the processing described below to make the mean of thedetected object sequence zero, and then uses these detected objectsequence that has had this processing implemented, in later processing.

When{q _(i)}: detected object sequence prior to processing (0<=i<n)

${{ave}\text{:}} = {\frac{1}{n}{\sum\limits_{i = 0}^{n - 1}q_{i}}}$is determined and the average is made zero by q_(i):=q_(i)−ave (0<=i<n).

According to the present embodiment, the mean of the detected objectsequence becomes zero and each item has a value that is either positiveor negative. This means that when the values for the correlation areadded later, correlation values other than those having a valid peak forthe position marker detection information are kept low so that whencompared to those embodiments for which this processing is notperformed, it becomes possible to perform detection at a better accuracyfor valid peaks of the position marker detection information.

Eighteenth Embodiment

The following is a description of the detected object sequencegenerating portion of the watermark detection portion according to aneighteenth embodiment of the present invention. Those portions notdescribed in the following are the same as portions of the previouslydescribed embodiments two through seventeen.

The detected object sequence generating portion of the watermarkdetection portion according to the previously described embodiments twothrough seventeen performs final stage processing to generate a detectedobject sequence as previously described for each of the embodiments,performs processing as described below so that the average for thedetected object sequence is zero, and then uses this detected objectsequence that has had this processing implemented, in later processing.

When{q _(i)}: detected object sequence prior to processing (0<=i<n),

${{ave}\text{:}} = {\frac{1}{n}{\sum\limits_{i = 0}^{n - 1}q_{i}}}$is determined and the average is made zero by q_(i):=q_(i)−ave (0<=i<n).

According to the present embodiment, the average of the detected objectsequence becomes zero and each item has a value that is either positiveor negative. This means that when the values for the correlation areadded later, correlation values other than those having a valid peak forthe symbol detection information are kept low so that when compared tothose embodiments for which this processing is not performed, it becomespossible to perform detection at a better accuracy for valid peaks ofthe symbol detection information.

Nineteenth Embodiment

The following is a description of the offset information generatingportion of the position marker detection portion according to anineteenth embodiment of the present invention. In the followingdescription, those portions not described are the same as those of thepreviously described second through eighteenth embodiments.

FIG. 106 is a flow chart showing the process of the offset informationgenerating portion of the position marker detection portion according tothe nineteenth embodiment of the present invention.

Step 5100) The offset information generating portion inputs the positionmarker detection information and, fist of all, determines the maximumvalue 0 max in all of the position marker detection information.

Step 5200) Then a threshold value beta which has been determinedbeforehand is used to separate the processing as follows. There is ashift to Step 5300 when 0 max<beta and a shift to Step 5400 otherwise.

Step 5300) A detection result indicating that the detection of theoffset information has failed is output externally to the offsetinformation detection apparatus, and the process is terminated.

Step 5400) The offset candidate information (a, b) when the maximumvalue 0max is taken is output as offset information and sent to thewatermark detection portion.

According to the nineteenth embodiment described above, detection doesnot continue unless the position marker detection information, that is,the value of the correlation between the position marker sequence andthe detected object sequence is above the threshold value beta. Thismeans that detection is not attempted and the output of an erroneousdetection result is thus prevented in cases such as when the detectedobject image is an image that has no embedded information, or whendetection is not possible due to severe damage to the embedded image,thereby increasing the reliability of the output detection result.

Twentieth Embodiment

The following is a description of the detection result generatingportion of the watermark detection portion according to a twentiethembodiment of the present invention. Those portions not described in thefollowing are the same as those of the previously described 2nd through19th embodiments.

FIG. 107 is flow chart showing the process of the detection resultgenerating portion of the watermark detection portion according to thetwentieth embodiment of the present invention.

Step 6100) The detection result generating portion inputs the symboldetection information and, first of all, in the sequence generatingportion that generates the symbol position sequence for each symbolposition, divides the symbol detection information for each symbolposition j.

Step 6200) The maximum value s_(max) ^((j)) of the sequence for eachj'th (1<=j<J) symbol position is determined and the processing branchesas follows depending upon a predetermined threshold value gamma.

Step 6300) There is a shift to Step 6400 when s_(max) ^((j))<gamma,otherwise there is a shift to Step 6500.

Step 6400) A detection result indicating that detection of a watermarkembedded in the detected object image has failed is output and allprocessing in the detection result generating portion is terminated.

Step 6500) When s_(max) ^((j))>gamma, the symbol candidate ccorresponding to the maximum value for s max<(j)> is made the j'thdetected symbol s_(j) (1<=j<J).

Step 6600) After all s_(j) have been determined, is transformed symbolexpression is transformed into a watermark expression (with, forexample, the inverse transform corresponding to the transform in thefirst embodiment having four symbols (with the values of the foursymbols, where the value of each symbol is from 0 &tilde& 255) beingregarded as ASCII code in processing of conversion into four 8-bitcharacters), and the detection results is generated and output.

According to the twentieth embodiment described above, detection doesnot continue unless the symbol detection information, that is, the valueof the correlation between each symbol marker sequence and the detectedobject sequence, is above the threshold value gamma. This means thatdetection is not attempted and an output of an erroneous detectionresult is thus prevented in cases such as when the detected object imageis an image that has no embedded information, or when detection is notpossible due to severe damage to the embedded image, thereby increasingthe reliability of the output detection result.

Twenty-first Embodiment

Finally, the following is a description of a twenty-first embodiment ofthe present invention. Those portions not described in the following arethe same as portions of the previously described first through twentiethembodiments.

With the present embodiment, the spread sequence generator of theembedding sequence generator in the first embodiment, and the positionmarker sequence generating portion and spread sequence generator for thesymbol sequence generating portion of the watermark detection portion ofthe twentieth embodiment use sequences (such as random sequencescomprising either the two values of “+1” or “−1” obtained using a k'thdegree generation polynomial expression (where k is a sufficiently largeinteger) such as that disclosed in pp. 128 of “Symbol Logic” (Shokohdoh)by Miyagawa et al., successively generated at random using either valuesof +1 or −1 at respective probabilities of ½).

In addition, with the present embodiment, the following is used as thecalculation formula for determining the correlation in the symboldetection information generating portion of the symbol detection portionof the watermark detection portion in the twentieth embodiment.

When there is

-   {pi}: symbol sequence (0<=i<n)-   {qi}: detected object sequence (0<=i<n), the value of the    correlation for the two sequences is

${{corr}\text{:}} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i}^{(j)} \cdot q_{i}} \right)}{\sqrt{\sum\limits_{i = 0}^{n - 1}q_{i}^{2}}}$

The distribution of the value of the correlation in the symbol detectioninformation generating portion is now considered.

$\frac{q_{i}}{\sqrt{\sum\limits_{i = 0}^{n - 1}q_{i}^{2}}}\mspace{14mu}\left( {0 \leq i < n} \right)$is a sequence that obeys a distribution having an average whichcalculate each item of the sequence, to be zero average value (accordingto the eighteenth embodiment) and variance of 1/n.

In addition, pi (0<=i<n) has the values of +1 or −1, each with arespective probability of ½, and obeys a distribution with an average of0 and a variance of 1. If n is sufficiently large,

$\frac{p_{i} \cdot q_{i}}{\sqrt{\sum\limits_{i = 0}^{n - 1}q_{i}^{2}}}\mspace{14mu}\left( {0 \leq i < n} \right)$becomes a sequence obeying a distribution with an average of 0 and witha variance of 1. Here, using the central limit theorem of probabilitystatistics when n is sufficiently large,

${{corr}\text{:}} = \frac{\sum\limits_{i = 0}^{n - 1}\left( {p_{i}^{(j)} \cdot q_{i}} \right)}{\sqrt{\sum\limits_{i = 0}^{n - 1}q_{i}^{2}}}$obeys a normal distribution with an average of 0 and a variance of 1.FIG. 108 is a graph (n=1024) showing the theoretical values N (0, 1) andthe corr values according to a computer simulation of the twenty-firstembodiment of the present invention, and from this, it can be seen that,as assumed, corr is N (0, 1).

Once it is known that corr is N (0, 1), the threshold value gamma in thetwentieth embodiment can be determined by probability (a scaleindicating the degree to which peaks have meaning).

For example, a probability of 99.999% (which makes 10⁻⁹ the probabilityof a peak accidentally appearing above the threshold value) gives athreshold value gamma=4.26489 on a normal distribution table at thattime. FIG. 109 is a graph of symbol detection information according to acomputer simulation of the twenty-first embodiment of the presentinvention. As can be seen from the figure, the symbol values thatexpress “A”, “B”, C” and “D” as the result of detection of the foursymbols (with each symbol having a value of from 0 &tilde& 255) allappear as significant peaks. The previously mentioned gamma is used toevaluate the degree of significance that a peak has (i.e, not anaccidental value). In the example shown in FIG. 109, the value of eachof the peaks is more than 4.26489 and so it can be judged to aprobability of more than 99.999, that the peaks are significant.

According to the twenty-first embodiment, the distribution of the symboldetection information can be a normal distribution with an average of 0and variance of 1 and so it is possible to specify the certainty ofsymbol detection. This means that it is possible to determine the degreeof certainty of the detection result, increase the reliability of thedetection result and improve the convenience.

To test the effectiveness of the proposed method, a computer simulationwas run. The three test images were 512×512 pixels, 8-bit gray-scaleimages (Lena, Sailboat, and Baboon). The parameter values used in thesimulation were N=128, n=1023, alpha=1.4, M=256. The value of (u n, v n)were selected from a medium frequency band specified by

$16 \leq \sqrt{u_{2}^{2} + v_{2}^{2}} \leq 32$and 32-bit ASCII text (such as “ABCD”) was used.

The following is a description of the image quality of watermarkedimages.

FIG. 110 is diagram showing the PSNR when the embedding intensity(power) of the present invention was changed. The values for “power”shown in graph of FIG. 110 are relative to “power”=xi. Thecorrespondence of PSNR to “power” varies from image to image due of theeffect of local weighting.

Parallel displacement and cutting are =42.107873). The offset responsepeak (14.761541) was detected at the offset (0,0). The symbol responsepeaks (11.180982 to 9.108589) were also detected for each symbol (‘A’,‘B’, ‘C’, ‘D’) in the watermarked image, indicating a successfulwatermark detection.

Next, there was an attempt at detecting watermark from a partial imagecut from each image. FIG. 112 shows the offset detect success ratio (forwhen the correct offset was detected) when the size N×N of the partialimage (having 50 start points chosen at random for each size) is changedand the symbol detect success ratio (for when all symbols were correctlydetected and the four peak values had a minimum value larger than thethreshold value of 4.26489). It is possible with almost total certaintyto detect watermark on a partial image larger than N=256. The watermarkis embedded in each block of 128×128 pixels bus as shown in FIG. 113(A), images that include an edge have several large frequency componentvalues that create a large amount of noise due to the original image asdescribed before, and this is thought to have caused detect failure.Conversely, there was success with a comparatively flat image as shownin FIG. 113 (B), or with detect for images such as textured images. Whenthere was detect using a differential with the original image, the noisedue to the original image was cancelled, leading to successful detect.

The following is a description of the JPEG compression.

An attempt was made to detect watermark from an image obtained fromirreversible JPEG compression of an image (Lena, sailboat, baboon,power=xi) having a watermark.

FIG. 114 shows the minimum value for the symbol response peak and theoffset response peak value when the quality parameter was changed. Thelines in the graphs of that figure represent successes attained beforestopping. If the threshold described previously is considered, theeffective robustness will probably be somewhat less than that shown inFIG. 114.

An attempt was made to detect watermark in a watermarked image (Lena,power=xi) that had undergone grayscale level degradation. In the case ofreduction to a black and white image, the offset response peak value3obtained from a Floyd-Steinberg dithered image (FIG. 115 (A)) was13.616614 and the symbol response peaks ranged from 9.395720 &tilde&6.825329 and the watermark was successfully detected. In the case of asimple quantization (FIG. 115 (B)), the watermark was also successful,with an offset response peak of 10.388254 and symbol response peaks inthe range from 8.133438 to 5.680073.

The following is a description of detect from a printed picture.

An image having a watermark (Lena, power=xi) was printed using a printerand an attempt was made to detect the watermark from an image that wasread by a scanner. The watermarked image was converted to 72 dpiPostScript data and printed out on a black-and-white laser printer(RICOH SP-10PS Pro/6F), 600 dpi. The printed image was then scanned(EPSON GT-6000) to acquire a 72 dpi in 16-bit grayscale image. Thescanned image was reduced to 8-bit grayscale and the watermark detectionwas performed on that image. In this case, the watermark detection wassuccessful, with an offset response peak value of 9.080504 and symbolresponse peak values ranging from 8.139693 to 5.615208. The combinationof printer and scanner resulted in a slight change in the aspect ratio.compensating for that aspect ratio change resulted in successfuldetection with an offset response peak value of 11.701824 and symbolresponse peak values ranging from 8.807638 to 6.623429.

We attempted to detect watermarks of two watermarked image (Lena andSailboat, both with power=xi) in an image that was a 1:1 mixture of thetwo images (FIG. 116), using the respective keys of the two images. Itwas possible to detect the two different watermarks in the single mixedimage, with an offset response peak value of 9.49749 for Lena and9.883106 for the sailboat image and symbol response peak values rangingfrom 8.102563 to 6.325033 for the woman image and from 9.661891 to7.285404 for Sailboat.

The following is a description of the detect processing time.

The offset search time using the method proposed by the presentinvention is N<2> and although a complete search is performed, butcompared to a simple full search in which the block is resampled and adiscrete Fourier transform is performed for each offset candidate, theamount of processing required for one search is small. Also, theprocessing can be speeded up by using a table of pre-calculated valuesfor the computation of e<−ix> in the search processing. Computersimulations of the invention and the simple full search described aboveshow that the ratio of processing times is 1:65. The discrete Fouriertransformation was performed on 128×128 pixel blocks using the FastFourier Transform (FFT).

Twenty-second Embodiment

FIG. 117 is a diagram showing a configuration of a degree of local imagecomplexity generating portion of a water mark embedding apparatusaccording to a twenty-second embodiment of the present invention. Thedegree of local image complexity generating portion 3010 shown in thefigure has an edge/texture component value image generating portion3110.

FIG. 118 is a flow chart showing the process of the degree of localimage complexity generating portion according to the twenty-secondembodiment of the present invention.

The degree of local image complexity generating portion 3010 inputs aninput image 10 (Step 22110), generates an edge/texture component valueimage generating portion 3110 generates an edge/texture component valueimage 3111 from the input image 10 (Step 22120), and outputs theedge/texture component value image as the degree of local imagecomplexity 20 (Step 22130).

In more detail, the edge/texture component value image generatingportion 3110 uses the following procedure to create the edge/texturecomponent value image.

FIG. 119 is a flow chart showing the process of the edge/texturecomponent value image generating portion according to the twenty-secondembodiment of the present invention.

Step 22121) The edge/texture component value image generating portion3110 expresses the input image 10 as{p _(ij)} (0<=i<Width, 0<=j<Height)Step 22122 onward is repeated for0<=i<Width, 0<=j<Height.

Step 22122) The edge/texture component value image generating portion3110 zeroes the count of the differential counter.

Step 22123) If, for −1<=k<=1, −1<=h <=1,

|p_(ij)−p_(i+k, j+h)|>threshold value then there is shift to Step 22124,and if not, this processing is repeated until (k, h) (−1, −1) &tilde&(k, h).

Step 22125) The value of the differential counter after the aboveprocessing of Step 22123 and Step 22124 has been repeated, becomes thevalue of the (i, j) coordinates of the edge/texture component valueimage. Expressing this as a formula givese_(ij)=countwhere {e_(ij)}: edge/texture component value image (0<=i<Width,0<=j<Height)

According to the twenty-second embodiment of the present invention asdescribed above, it is possible to generate a degree of local complexityfor an image having a large value in the case of input image 10 having asmall flat portion or when there is a edge or texture domain.

In addition, as shown in FIG. 120, the use of a threshold and adifferential counter enables the generation of a degree of localcomplexity for an image having a similarly large value for images havingsharp edges and soft textures.

Twenty-third Embodiment

The following is description of the processing for a degree of localimage complexity generating portion of a watermark embedding apparatusof the twenty-third embodiment of the present invention. FIG. 121 is adiagram showing the configuration of the degree of local imagecomplexity generating portion according to the twenty-third embodimentof the present invention.

The degree of local image complexity generating portion 3020 shown inthe figure comprises a edge/texture component value image generatingportion 3210 of the twenty-second embodiment as shown in FIG. 117, andin addition, a texture degree index generating portion 3220 and anup-sampler 3230.

FIG. 122 is a flow chart showing the process of the degree of localimage complexity generating portion according to the twenty-thirdembodiment of the present invention.

The degree of local image complexity generating portion 3020 inputs theinput image 10 (Step 23210) and an edge/texture component value imagegenerating portion 3210 generates the edge/texture component value image3201 from the input image 10 (Step 23220).

Next, in the texture degree index generating portion 3220, a texturedegree index 3202 is created from the edge/texture component value image3201, and then the up-sampler 3230 up-samples the texture degree index3202 (Step 23230), makes it the same size as the input image 10, andoutputs it as the degree of local image complexity 20 (Step 23240).

The following is a description of the process of the texture degreeindex generating portion 3220 described above. FIG. 123 is a flow chartshowing the process of the texture degree index generating portionaccording to the twenty-third embodiment of the present invention.

Step 23231) The texture degree index generating portion 3220 divides theedge/texture component value image 3201 into blocks of n×n pixels (withthe edge/texture component value image, which is the result of thisdivision, being P×Q blocks).

The pixels in the (p, q)'th block are b ij (0<=i<n, 0<=j<n).

Step 23232) The (p, q)'th texture degree index index_(pq) is zeroed.

Step 23233) Index_(pq):Index_(pq)+b_(ij) ^((p,q))with the processing repeated for(i, j)=(0,0) &tilde& (n−1, n−1)and when this ends, the processing from Step 23232 onward is repeatedfor(p, q)=(0,0) &tilde& (P−1, Q−1).

In other words, making

-   {b_(ij)(p,q)}: block pixel value of the (p, q)'th edge/texture    component image (0<=i<n, 0<=j<n),    means that the texture degree index index pq of the (p, q)'th block    ((0<=p<P, 0<=q<Q) can be obtained by the following formula.

${{index}_{pq}\text{:}} = {\sum\limits_{i = 0}^{n - 1}{\sum\limits_{j = 0}^{n - 1}b_{ij}^{({pq})}}}$

The following is a description of the process of the up-sampler 3230 inthe present embodiment.

FIG. 124 is a diagram describing the process of an up-sampler accordingto the twenty-third embodiment of the present invention. The up-sampler3230 inputs the texture degree index 3202 (P×Q pixel size) and magnifiesit N times laterally and longitudinally so to generate and output adegree of local image complexity (of size Width×Height) of an image thesame size as the input image 10.

As has been described above, according to the present embodiment, blocksof those block groups obtained by division of an edge/texture componentvalue image into n×n pixels that include many large values, take largevalues for the texture degree index, while blocks that include manysmall values take small values for the texture degree index.

FIG. 125 is a diagram showing an edge/texture component value image anda texture degree index according to the twenty-third embodiment of thepresent invention. As shown in the figure, a simple edge portion (thetop right portion of the same figure) within the edge/texture componentvalue image 3201 has a small number of points having large valuesincluded in the block and so these have correspondingly small values forthe texture degree index. This means that when compared to thetwenty-second embodiment, the present embodiment enables the generationof an image degree of local image complexity having higher values.

Twenty-fourth Embodiment

The following is description of a twenty-fourth embodiment of thepresent invention.

FIG. 126 is a flow chart showing the process of a degree of local imagecomplexity generating portion of a watermark embedding apparatusaccording to the twenty-fourth embodiment of the present invention.

When the degree of local image complexity generating portion 3020 inputsthe input image 10 (Step 24310), the edge/texture component value imagegenerating portion 3210 generates the edge/texture component value image3201 from the input image 10 (Step 24320). Next, in the texture degreeindex generating portion 3220 the texture degree index 3202 is createdfrom the edge/texture component value image 3201 and then the up-sampler3230 up-samples the texture degree index 3202 (Step 4330), makes it thesame size as the input image 10 and outputs it as the degree of localimage complexity.

FIG. 127 is flow chart showing the process of the texture degree indexgenerating portion according to the twenty-fourth embodiment of thepresent invention.

Step 24331 &tilde& Step 24333) The texture degree index generatingportion 3220 uses a value mapped by a predetermined function f(x) forthe determined texture degree index (indexpq), as the new texture degreeindex. Expressing this as a formula gives the following.index_(pq):f(index_(pq)) (0<=p<P, 0<=q<Q)

According to the twenty-fourth embodiment, using the function to map thetexture degree index 3202 obtained by the previously describedtwenty-third embodiment enables a value that is in agreement with morevisual characteristics.

Twenty-fifth Embodiment

The following is a description of a degree of local image complexitygenerating portion of a watermark embedding apparatus of a twenty-fifthembodiment of the present invention.

FIG. 128 is a diagram showing the configuration of the degree of localimage complexity generating portion according to the twenty-fifthembodiment of the present invention. The degree of local imagecomplexity generating portion 3400 shown in the figure comprises anedge/texture component value image generating portion 3410, a texturedegree index generating portion 3420, and a texture component valueimage generating portion 3430. The texture component value imagegenerating portion 3430 generates and outputs a texture component valueimage 3403 from a edge/texture component image 3401 and a texture degreeindex 3402.

FIG. 129 is a flow chart showing the process of the degree of localimage complexity generating portion according to the twenty-fifthembodiment of the present invention.

When the degree of local image complexity generating portion 3400 inputsthe input image 10 (Step 25410), the edge/texture component value imagegenerating portion 3410 generates the edge/texture component image 3401from the input image 10 (Step 25420).

Next, the texture degree index generating portion 3420 generates thetexture degree index 3402 from the edge/texture component image 3401using the method of either the twenty-third or the twenty-fourthembodiment as the creation method (Step 25430). Then, the texturecomponent value image generating portion 3430 generates the texturecomponent value image 3403 from the edge/texture component image 3401and the texture degree index 3402 (Step 25440) and outputs this as thelocal degree of image complexity (Step 25450).

The following is a description of the texture degree index generatingportion 3420.

FIG. 130 is flow chart showing the process of the texture componentvalue image generating portion according to the twenty-fifth embodimentof the present invention.

Step 25441) The texture component value image generating portion 3430divides the edge/texture component 3401 into blocks of n×n pixels (withthe edge/texture component value image, which is the result of division,consisting of P×Q blocks). Step 25442 is performed for each block.

Step 25442) The following is a description of the processing for the (p,q)'th block (0<=p<P, 0<=q<Q) of the texture component value imagegenerating portion 3430.

Taking the block pixel value (0<=i<n, 0<=j<n) of the {b_(ij) ^((p,q))}:(p, q)'th edge/texture component image, the texture component valueimage generating portion 3430 uses the following formula to determinethe (p, q)'th texture component value block {b′_(ij) ^((p,q))}, (0<=i<n,0<=j<n).b′ _(ij) ^(( p,q)):=index _(pq)·b _(ij) ^((p,q))

Step 25443) After this processing has been completed for all blocks,outputs the texture component value block 3403, which provides sameposition with edge/texture component value image 3401.

The following is a description of the image processing of the presentembodiment, with reference to FIG. 131. The input image 10 shown in thefigure comprises a background (of uniform pixel values), a sun (havingan edge, and with a uniform interior), a tree trunk (having a lighttexture) and leaves (having a strong texture). In the edge/texturecomponent image 3401 (with values larger for brighter portions), thehandling is the same for both edges and textures. The portions for thetree trunk and leaves and the edge portion of the sun have largelydifferent values for the edge/texture components. This is because of theuse of the differential counter.

In the texture degree index 3402, the method of creating gives a smallvalue for blocks that have little edge/texture component. Because ofthis, the texture degree index is small for the portions of the sun thatdo not have an edge. Conversely, the portions for the tree trunk andleaves have a large edge/texture component within the block and so havelarge values for the texture degree index 3402.

In the texture component value image 3403 (with brighter portions havinglarger values), the edge is weak, ad the texture becomes stronger whichis in agreement with the objective. In addition, when compared to theoutput of the twenty-third embodiment, the block distortion is improved,and it is possible to generate a degree of image complexity for theimage at a higher accuracy.

Twenty-sixth Embodiment

The following is a description of a watermark embedding apparatus of atwenty-sixth embodiment.

FIG. 132 is a diagram showing the configuration of the watermarkembedding apparatus according to the twenty-sixth embodiment of thepresent invention. The watermark embedding apparatus 3500 comprises adegree of local image complexity generating portion 3510, a watermarkpattern generating portion 3520, and an image addition portion 3530. Thewatermark embedding apparatus 3500 inputs an input image 51, a watermark52, a key 53 and an intensity parameter 54.

FIG. 133 is a flow chart showing the process of the watermark embeddingapparatus according to the twenty-sixth embodiment of the presentinvention.

Step 25610) First of all, the degree of local image complexitygenerating portion 3510 generates a degree of local image complexity(e_(ij)) from the input image 51 (p_(ij)). The degree of local imagecomplexity ideally indicates the amount by which object image values canbe changed when visual stimulation due to changes in pixel values isless than a certain amount. For example, this embodiment any one of thedegree of local image complexity generating portion previously describedfor the twenty-second through twenty-fifth embodiments.

Step 26520) The watermark pattern generating portion 3520 uses thewatermark 52 and the key 53 as the basis for generating a watermarkpattern w_(ij) 3502.

Step 26530) In the image addition portion 3530, the watermark pattern3502 is adaptively added to the degree of local image complexityaccording to the following formula.p′ _(ij):=p _(ij)+powers·e _(ij) ·w _(ij)where,

-   {p′_(ij)}: image having embedded information (0<=i<width,    0<=j<Height)-   {p_(ij)}: input image (0<=i<width, 0<=j<Height)-   {w_(ij)}: watermark pattern (0<=i<width, 0<=j<Height)

Step 26540) The image addition portion 3530 outputs the image p ijhaving the watermark embedded.

The following is a description of the watermark pattern 3502 in Step26530.

A complex matrix F of N×N pixel size is prepared with a zero matrix asan initial value.

The k'th embedding coefficient position information Lx=(xk,yk,zk)(generated from the key) is used to change F(u, v).

When z k is a value that expresses a real number component, m k(generated from the key and the watermark) is added to the real numbercomponent of F(x k,y k). In addition, m k is add to the real numbercomponent of F (N−x k, N−y k) so as to maintain the symmetry of theFourier transform coefficient. Expressing this as a formula givesF(xk,yk):=F(xk,yk)+mk·alpha F(N−xk,N−yk):=F(N−xk,N−yk)+mk·alphawhere alpha is a parameter corresponding to the intensity of the basicwatermark pattern.

When z k is a value that expresses an imaginary number component, m k isadded to the imaginary number component of F (x k, y k). In addition, mk is subtracted from the imaginary number component of F(N−x k, N−y k).Expressing this as a formula givesF(xk,yk):=F(xk,yk)+mk·alpha·i F(N−xk,N−yk):=F(N−xk,N−yk)−mk·alpha·i(where i is the imaginary number unit).

This is successively performed for k=0 . . . , n−1 and the obtainedcoefficient matrix F(u, v) has an inverse Fourier transform performed togive the basic watermark pattern.

According to the twenty-sixth embodiment described above, the degree oflocal complexity is used to weight the watermark pattern which is addedto the input image to obtain the image having the watermark embedded andso it becomes possible to suppress the visual image deterioration thataccompanies embedding, and when compared to conventional technologies,to improve the robustness when there is deterioration of the image tothe same degree.

Twenty-seventh Embodiment

The following is a description of a watermark embedding apparatus of atwenty-seventh embodiment of the present invention.

FIG. 134 is a diagram showing the configuration of the watermarkembedding apparatus according to the twenty-seventh embodiment of thepresent invention. The watermark embedding apparatus 3600 shown in thefigure comprises a block division portion 3610, a degree of local imagecomplexity generating portion 3620, an adaptive watermark patterngenerating portion 3630, a basic watermark pattern generating portion3640 and an image addition portion 3650.

The watermark embedding apparatus 3600 inputs an input image 61, awatermark 62, a key 63 and an intensity parameter 64.

FIG. 135 is a flow chart showing the process of the watermark embeddingapparatus according to the twenty-seventh embodiment of the presentinvention.

Step 27610) The block division portion 3610 divides the input image 61(comprising Width×Height pixels), into blocks 3601 of N×N pixel size.

Step 27620) The divided blocks 3601 are used by the degree of localimage complexity generating portion 3620 to generate a degree of localimage complexity 3603 of a block size. In the same manner as thepreviously described twenty-fifth embodiment, the degree of local imagecomplexity 3603 ideally expresses the amount by which the symmetricalpixel values can be changed when the visual stimulation due to changesin the image pixels is lower than a certain level. For example, any ofthe degree of local image complexity generating portion described forembodiments twenty-two through twenty-five can be used.

Step 27630) The basic watermark pattern generating portion 3640 uses thewatermark 62 and the key 63 to generate a basic watermark pattern 3604.The basic watermark pattern 3604 is the same as that described as the“watermark pattern” in the twenty-sixth embodiment. Specifically, thisis expressed by the following formula.

A complex matrix F of N×N size is prepared with a zero matrix as aninitial value.

The k'th embedding coefficient position information Lk=(xk,yk,zk)(generated from the key) is used to change F (u, v).

When z k is a value that expresses a real number component, m k(generated from the key and the watermark) is added to the real numbercomponent of F (x k,y k). In addition m k is add to the real numbercomponent of F(N−x k, N−y k) so as to maintain the symmetry of theFourier transform coefficient. Expressing this as a formula givesF(xk,yk):=F(xk,yk)+mk·alpha F(N−xk,N−yk):=F(N−xk,N−yk)+mk·alphawhere, alpha is a parameter given to the intensity of the basicwatermark pattern.

When z k is a value that expresses an imaginary number component, m k isadded to the imaginary number component of F(x k,y k). In addition, m kis subtracted from the imaginary number component of F (N−x k,N−y k).Expressing this as a formula givesF(xk,yk):=F(xk,yk)+mk·alpha·i F(N−xk,N−yk):=F(N−xk,N−yk)−mk·alpha·i(where i is the imaginary number unit).

This is successively performed for k=0 . . . , n−1 and the obtainedcoefficient matrix F(u, v) has an inverse Fourier transform performed togive the basic watermark pattern.

Step 27630) Furthermore, the adaptive watermark pattern generatingportion 3630 generates the adaptive watermark pattern 3602.

The method of determining the adaptive watermark pattern 3602 isexpressed by the following formula.

${p^{\prime}\text{:}} = {p_{ij} + {{power} \cdot \frac{{\beta \cdot a_{ij} \cdot \left( {e_{ij} - e_{\min}} \right)} + {\left( {e_{\max} - e_{ij}} \right) \cdot b_{ij}}}{e_{\max} - e_{\min}}}}$where

-   {p′_(ij):}: block having embedded information (0<=i<N, 0<=j<N-   {p_(ij):}: block (0<=i<N, 0<=j<N-   {e_(ij):}: degree of local image complexity (0<=i<N, 0<=j<N)-   {a_(ij):}: adaptive watermark pattern (0<=i<N, 0<=j<N)-   {b_(ij):} basic watermark pattern (0<=i<N, 0<=j<N)-   power: intensity parameter-   e max: maximum value of the area according to the formula defining    the degree of local image complexity-   e min: minimum value of the area according to the formula defining    the degree of local image complexity-   beta: adaptive watermark pattern emphasis ratio

Step 27660) After the blocks 3605 having the embedded watermark havebeen generated for all blocks 360, the blocks 3605 having the embeddedwatermark are arranged at the original block positions and an image 65having the embedded watermark is obtained.

The following is a description of the adaptive watermark patterngenerating portion 3630 in the present embodiment.

The adaptive watermark pattern generating portion 3630 emphasizes theorthogonal transform coefficient corresponding to the basic watermarkpattern 3604, in accordance with the value of the amplitude of theorthogonal transform coefficient of the block that is currently beingreferred to.

FIG. 136 is a flow chart showing the process of the adaptive watermarkpattern generating portion according to the twenty-seventh embodiment ofthe present invention.

Step 27461) The blocks that have been divided by the block divisionportion 3610 undergo a discrete Fourier transform to obtain a blockcoefficient matrix G (u, v).

Step 27642) The basic watermark pattern undergoes a discrete Fouriertransform to generate a complex watermark coefficient matrix F (u, v)(0<=u<N, 0<=v<N).

Step 27643) When |G(u, v)|<alpha for (u,v)=(0,0) &tilde& (N−1, N−1),there is a shift to Step 27644, and if not, there is a shift to Step27645.

Step 27644) When |G(u, v)|<alpha gamma:=alpha and there is shift to Step27646.

Step 27645) When |G(u, v)|>/=alpha gamma:=|G(u, v)|. Moreover, the alphain Step 27644 and Step 27645 is threshold value that is determinedbeforehand.

Step 27646) F′(u,v):=F(u,v)·gamma.

Step 27647) F′(u,v) undergoes a discrete Fourier transform and is outputas the adaptive watermark pattern 3602.

As has been described above, according to the present embodiment and asshown in FIG. 137, it is possible to perform image embedding using awatermark pattern that accurately reflects a local design in the inputimage. This is to say that there is no correlation between the design ofthe original block 3601 (diagonal lines of the left-front fan-shapedportion) and the basic watermark pattern 3604, but the adaptivewatermark pattern 3602 accurately reflects the design of the block 3601.These degrees of local image complexity are used to give a weighting andadding enables the embedding of watermark in a shape that accuratelyreflects the original design of the block 3601 and that has a strongpower.

In addition, the process and configuration of the embodiment describedabove is configured as a program that can easily realize the presentinvention by storage in a device connected to a computer used as aninformation embedding apparatus or a watermark embedding apparatusstorage in a portable storage medium such as a floppy disk or CD-ROM orthe like and installed to implement the present invention.

Twenty-eighth Embodiment

With the present embodiment, it is possible to realize the watermarkembedding apparatus described in the first through twenty-seventhembodiments, by an integrated circuit as shown in FIG. 138. Theintegrated circuit shown in FIG. 138 comprises a memory portion 1, amicroprocessor portion 2, and an interface portion 3 having an externalinterface. Moreover, this figure only shows the main portion but alsoincludes other circuits. The program stored in the memory portion 1 isrun by the microprocessor portion 2. Various other configurations arealso possible for the integrated circuit.

In addition, it is also possible to perform the watermark processing ofthe present invention by incorporating these integrated circuits intovarious devices such as a video camera and a playback device, forexample.

As has been described above, according to the present invention, it ispossible to have the following effects and applications.

For the authors, the purpose is to protect copyright over the content ofthe information and so the watermark must have robustness with respectto editing by various types of users, while for the users, it must bepossible to use the content of the information while being unaware ofthe watermark and so it must not be possible to sense any deteriorationof images that have undergone watermark processing.

According to the present invention, improving the image quality and therobustness over that of the conventional technology enables a copyrightprotection system to function more effectively, and enable authors tosecurely supply an information content, thereby promoting the flow ofinformation over networks.

In a content distribution system, the present invention gives a contentID so as to uniquely identify the content, and this content ID is thenembedded in the content to link the information of the author of thecontent with user conditions and the like, so that use in a contentmanagement system encourages the correct use of the content, and on theside of those holding rights, guarantees that one hold rights to thecontent.

In addition, the present invention embeds user information when thecontent is distributed so that is possible to suppress illegal copying.

Futhermore, embedding copy management signals used by DVD and the likecan realize more rigid copy protection than at present.

Moreover, the present invention is not limited to the embodimentsdescribed above, as various modifications and applications are possiblewithin the scope of the claims.

1. A watermark detection method for detecting an embedded watermark in adetected object image, which watermark is imperceptible visually, themethod comprising: a step for cutting a pixel block from an arbitraryposition of said detected object image; a step for obtaining acoefficient matrix by performing a discrete Fourier transform on saidblock; a step for generating detected object component positioninformation specified by a key; a step for multiplying a phasedifference of a coefficient due to an amount of parallel displacement,with each item of said detected object component position information,and generating a position marker sequence; a step for extracting offsetinformation which is the amount of parallel displacement when a startpoint of the embedded watermark is in agreement with a start point ofthe pixel block cut from the detected object image; and a step fordetecting said embedded watermark from said pixel block cut from thedetected object image on the basis of said offset information.
 2. Thewatermark detection method as claimed in claim 1, wherein said step forgenerating said detected object component position information from saidkey, comprising: a step for generating a random number sequence that hassaid key as an initial value; and a step for generating said detectedobject component position information from said random number sequence.3. The watermark detection method as claimed in claim 1, wherein saidstep for generating said position marker sequence, comprises: a step forgenerating a 0′th spread sequence that has said key as an initial value;and a step for outputting said spread sequence as said position markersequence.
 4. The watermark detection method as claimed in claim 1,wherein said step for extracting said offset information comprises: astep for generating offset candidate information; a step for cutting apixel block from said detected object image from a position of saidoffset candidate information; a step for performing a discrete Fouriertransform on said pixel block and generating a detected objectcoefficient matrix; a step for generating a detected object sequencefrom said detected object component position information and saiddetected object coefficient matrix; a step for grouping correlationvalues for said position marker sequence and said detected objectsequence along with said offset candidate information and generatingsaid position marker detection information; and a step for extractingoffset information for which the value of the correlation between saidposition marker sequence and said detected object sequence is maximum.5. The watermark detection method as claimed in claim 1, wherein saidstep for detecting said embedded watermark comprising: a step forcutting pixel block of N×N pixels from a position of said detectedobject image, which position has undergone parallel displacement by anamount of said offset candidate information; a step for performing adiscrete Fourier transform on said pixel block and generating a ,detected object coefficient matrix; a step for generating a detectedobject sequence from said detected object component position informationand said detected object coefficient matrix; a step for generatingsymbol detection information from said detected object sequence and saidkey; and a step for detecting, as a watermark, a detection result fromsaid each detected symbol of said symbol detection information.
 6. Thewatermark detection method as claimed in claim 5, wherein said step fordetecting, as said watermark, said detection result from said symboldetection information comprises: a step for generating a sequence foreach symbol position of said symbol detecting information; a step forselecting, as the detected symbol, a symbol candidate having a maximumvalue in the sequence for said each symbol position; and a step forperforming inverse symbol transform of said detection symbol andobtaining results of said detect.
 7. The watermark detection method asclaimed in claim 1, wherein said step for detecting said embeddedwatermark, comprising: a step for outputting a pixel block cut from saiddetected object image by cyclic shift of said cut pixel block, accordingto said offset information.
 8. The watermark detection method as claimedin claim 1, wherein said step for detecting said embedded watermark,comprising: a step for cutting pixel block of N×N pixels from saiddetected object image when a size of said detected object image is equalto or greater than N×N pixels; a step for, when the size of saiddetected object image is smaller than N×N pixels, determining an averagepixel value for a portion of said detected object image included when anN×N size pixel block is cut, filling a remaining empty portion of saidN×N size pixel block with said average pixel value, and generating afirst pixel block; and a step for performing cyclic shift of said fistpixel block and outputting said cyclic shifted first pixel block as apixel block.
 9. The watermark detection method as claimed in claim 1,wherein said step for detecting said embedded watermark, comprising: astep for dividing said detected object image into a pixel block from aposition corresponding to said offset information; a step for performinga discrete Fourier transform on said divided pixel block and generatinga detected object coefficient matrix; a step for generating a detectedobject sequence from said detected object component position informationand said detected object coefficient matrix; a step for generatingsymbol detection information from said detected object sequence and saidkey; and a step for outputting a detection result corresponding to saidsymbol detection information.
 10. The watermark detection method asclaimed in claim 1, wherein said step for detecting said embeddedwatermark, comprising: a step for dividing said detected object imageinto pixel blocks and performing cyclic shift said pixel blocksaccording to said offset information; a step for performing a discreteFourier transform on said pixel block that has undergone said cyclicshift, and generating a detected object coefficient matrix, and a stepfor generating a detected object sequence from said detected objectcomponent position information and said detection object coefficientmatrix, a step for generating symbol detection information from saiddetected object sequence and said key; a step for generating eachdetected symbol from said symbol detection information, and detecting awatermark from said each detected symbol.
 11. The watermark detectionmethod as claimed in claim 1, wherein said step for detecting saidembedded watermark, comprising: a step for dividing said detected objectimage into pixel blocks and performing cyclic shift of said pixel blocksaccording to the offset information wherein, pixel blocks around theedges of the detected object image contain empty portions, the emptyportions are filled with an average pixel value; a step for performing adiscrete Fourier transform on said pixel block and generating a detectedobject coefficient matrix; a step for generating a detected objectsequence from said detected object component position information andsaid detected object coefficient matrix; a step for generating symboldetection information from said detected object sequence and said key;and a step for generating each detected symbol from said symboldetection information, and detecting a watermark from said detectedsymbol.
 12. The watermark detection method as claimed in claim 1,wherein said step for generating said position marker sequence,comprising: a step for dividing said detected object image into blocksusing said using offset information, and a step for outputting anadditional block, which is the sum of corresponding pixel values of saidpixel blocks, as a pixel block.
 13. The watermark detection method asclaimed in claim 1, wherein said step for generating said positionmarker sequence, comprising: a step for dividing said detected objectimage into blocks; and a step for generating an addition block by addingcorresponding pixel values of said divided blocks, using an offset toperform cyclic shift of said additional block, and generating saidcyclic shifted additional block as a pixel block.
 14. The watermarkdetection method as claimed in claim 1, wherein said step for generatingsaid position marker sequence, comprising: a step for dividing saiddetected object image into block and, when a block around the edge ofsaid detected object image contains an empty portion, determining anaverage value of pixel values of the portion of the block includingdetected object image, and filling said empty portion with said averagevalue; a step for generating an additional block by adding correspondingto pixel values of said divided blocks; and a step for using an offsetto perform cyclic shift of said additional block and outputting saidcyclic shifted additional block as a pixel block.
 15. The watermarkdetection method as claimed in claim 4, wherein said step for generatingsaid position marker sequence, comprising; a step for determining anaverage value of said detected object sequence prior to generating saiddetected object sequence.
 16. The watermark detection method as claimedin claim 5, wherein said step for detecting said watermark, comprising:a step for determining an average value of said detected object sequenceprior to generating said detected object sequence.
 17. The watermarkdetection method as claimed in claim 1, wherein said step for generatingsaid position marker sequence, and extracting said offset information,comprising: a step for determining a maximum value of said positionmarker detection information, and when said maximum value is smallerthan a required threshold value, outputting offset detection failureinformation, and said required threshold value, outputting said offsetinformation corresponding to said maximum value.
 18. The watermarkdetection method as claimed in claim 1, wherein said step for detectingsaid watermark, comprising: a step for dividing symbol detectioninformation into that for each symbol position, and generating asequence for each symbol position; a step for determining a maximumvalue of said sequence for said each symbol position, and when saidmaximum value is smaller than a required threshold value, outputtingwatermark detection failure information, and when said maximum value isequal to or greater than said required threshold value, detecting asymbol corresponding to said maximum value; and a step for convertingfrom said detected symbol into a watermark expression.
 19. The watermarkdetection method as claimed in claim 18, wherein said required thresholdvalue is determined on the basis of a value of normal distributionfunction having an average of 0 and a variance of
 1. 20. A watermarkdetection method that detects an embedded watermark so that informationof contents is imperceptible visually, from a detected object imageembedded said watermark, comprising: a step for generating objectcomponent position information from key, a step for generating aposition marker sequence from said key, a step for detecting offsetinformation that expresses the degree to which a start point of anembedded watermark pattern is displaced from a start point of a pixelblock cut from said detected object image; and a step for detectingwatermark embedded in said pixel block cut from said detected objectimage using said offset information.
 21. The watermark detection methodas claimed in claim 20, wherein said step for generating objectcomponent position information, comprising: a step for generating arandom number sequence taking said key as an initial value, and a stepfor generating detected object component position information having thesame length as the length of an embedded embedding sequence using saidrandom number sequence.
 22. The watermark detection method as claimed inclaim 20, wherein said step for generating position marker sequence,comprising: a step for generating a spread sequence having a 0′th lengthand said key as an initial value, and outputting said spread sequence asa position marker sequence.
 23. The watermark detection method asclaimed in claim 20, wherein said step for generating position markersequence, comprising: a step for cutting a pixel block of a size of N×Npixels from said detected object image using said detected objectcomponent position information and said position marker sequence; a stepfor performing a discrete Fourier transform on said pixel block, andgenerating detection object coefficient matrix; a step for generating adetected object sequence from said detected object coefficient matrixand said detected object component position information; and a step forgrouping correlation values for said position marker sequence and saiddetected object sequence and generating said position marker detectioninformation.
 24. The watermark detection method as claimed in claim 20,wherein said step for generating position marker sequence comprises; astep for dividing said detected object image into blocks of N×N size,and a step for taking an added block that is the sum of pixel values ofall blocks, as a pixel block.
 25. The watermark detection method asclaimed in claim 20, wherein said step for detecting watermark,comprising: a step for cutting a pixel block from said detected objectimage using said detected object image, said detection object componentposition information, said offset information and said key; a step forperforming a discrete Fourier transform on said pixel block, andgenerating a detected object coefficient matrix, a step for generating adetected object sequence from said offset information said detectedobject coefficient matrix and said detected object component positioninformation; a step for generating symbol detection information from acorrelation value between said detected object sequence and a sequencegenerated from said key and symbol candidate information; a step forusing each symbol position of said symbol detection information as thebasis for detecting a symbol when the value of the correlation ismaximum; and a step for outputting a result of conversion from saiddetected symbol into a watermark format.
 26. The watermark detectionmethod as claimed in claim 20, wherein said step for generating saidposition marker sequence, comprising: when a pixel block of a size ofN×N pixels has been cut from said detected object image, in a case saidpixel block has an empty portion, determining an average of pixel valuesof a portion of said pixel of said pixel block including said detectedobject image, and filling said empty portion with said average value.27. The watermark detection method as claimed in claim 25, wherein saidstep for detecting said watermark, comprising: a step for dividing apixel block from said detected object image; a step for performing adiscrete Fourier transform on said pixel block and generating a detectedobject coefficient matrix; a step for generating a detected objectsequence from said offset information, said detected object coefficientmatrix and said detected object component position information; a stepfor generating a detected symbol from said detected object sequence andsaid key, and a step for detecting a watermark from said detectedsymbol.
 28. The watermark detection method as claimed in claim 27,wherein said step for detecting said watermark, comprising: when a pixelblock of a size of N×N pixels has been cut from said detected objectimage, in a case said pixel block has an empty portion, determining anaverage of pixel values of a portion of said pixel of said pixel blockincluding said detected object image, and filling said empty portionwith said average value.
 29. The watermark detection method as claimedin claim 20, wherein said step for detecting said position markersequence and said step for detecting said watermark, comprising: a stepfor dividing said detected object image into blocks of N×N pixel size;and a step for outputting an additional block, which is the sum ofrespective pixel values for all blocks, as a pixel block.
 30. Thewatermark detection method as claimed in claim 20, wherein said step fordetecting said watermark, comprising: when a pixel block of a size ofN×N pixels has been cut from said detected object image, in a case saidpixel block has an empty portion, determining an average of pixel valuesof a portion of said pixel of said pixel block including said detectedobject image, and filling said empty portion with said average value.31. The watermark detection method as claimed in claim 24, wherein saidstep for detecting said position marker sequence, comprising: a step forgenerating said detected object sequence, and calculating an averagefrom item of said detected object sequence so as to the average value tobe
 0. 32. The watermark detection method as claimed in claim 25, whereinsaid step for detecting said watermark, comprising: a step forgenerating said detected object sequence, and calculating an averagefrom item of said detected object sequence so as to the average value tobe
 0. 33. The watermark detection method as claimed in claim 27, whereinsaid step for detecting said watermark, comprising: a step forgenerating said detected object sequence, and calculating an averagefrom item of said detected object sequence so as to the average value tobe
 0. 34. The watermark detection method as claimed in claim 20, whereinsaid step for detecting said offset information, comprising: a step fordetermining a maximum value of said position marker detectioninformation; and a step for outputting offset detection failureinformation when a maximum of said position marker detection informationis smaller than a required threshold value, and outputting said offsetinformation when said maximum value is equal to or larger than saidrequired threshold value.
 35. The watermark detection method as claimedin claim 25, wherein said step for detecting said watermark, comprising:a step for dividing said symbol detection information for each symbolposition; a step for determining a maximum value of a sequence for eachsymbol position; and a step for outputting watermark detection failureinformation when said maximum value is smaller than a required thresholdvalue, and outputting a symbol candidate when said maximum value isequal to or larger than said required threshold value.
 36. The watermarkdetection method as claimed in claim 35, wherein said required thresholdvalue is determined according to a value of a normal distributionfunction and confidence value having a average of 0 and a variance of 1.37. A watermark detection apparatus for detecting an embedded watermarkin a detected object image, which watermark cannot be sensed visually,the apparatus comprising; detected object component specification meansfor generating detected object component position information from akey; position marker sequence generation means for generating a positionmarker sequence from the key; position marker detection means fordetecting said position marker sequence, and extracting a offsetinformation when a start point of the embedded watermark is in agreementwith a start point of a pixel block cut from a detected object image;and watermark detection means for detecting said embedded watermark fromsaid pixel block cut from said detected object image on the basis ofsaid offset information.
 38. The watermark detection apparatus asclaimed in claim 37, wherein said detected object componentspecification means, comprises: means for generating a random numbersequence that has said key as an initial value; and means for generatingsaid detected object component position information from said randomnumber sequence.
 39. The watermark detection apparatus as claimed inclaim 37, wherein said position marker sequence generation means,comprises: a means for generating a 0′th spread sequence taking said keyas an initial value, and outputting said spread sequence as saidposition marker sequence.
 40. The watermark detection apparatus asclaimed in claim 37, wherein said position marker detection means,comprises: means for generating offset candidate information, andcutting a pixel block from a position of said detected object image,which position is determined by said offset candidate information; meansfor performing a discrete Fourier transform on said pixel block andgenerating a detected object coefficient matrix; means for generating adetected object sequence from said detected object component positioninformation and said detected object coefficient matrix; means forgrouping said offset candidate information and a correlation value forsaid position marker sequence and said detected object sequence andgenerating position marker detection information; and means forextracting, as said offset information offset candidate information whenthe correlation value for said position marker sequence and saiddetected object sequence is maximum.
 41. The watermark detectionapparatus as claimed in claim 37, wherein said watermark detectionmeans, comprises: means for cutting a pixel block of N×N pixels from aposition of said detected object image, which position has undergoneparallel displacement by the amount of said offset candidateinformation; means for performing a discrete Fourier transform on saidpixel block and generating a detected object coefficient matrix; meansfor generating a detected object sequence from said detected objectcomponent position information and said detected object coefficientmatrix; means for generating symbol detection information from saiddetected object sequence and said key; means for generating eachdetected symbol from said symbol detection information; and means foroutputting, as a watermark, a detection result from said each detectedsymbol.
 42. The watermark detection apparatus as claimed in claim 41,wherein said watermark detection means, further comprises: means forgenerating a sequence for each symbol position of said symbol detectioninformation; and means for selecting, as the detected symbol, a symbolcandidate having a maximum value in the sequence for said each symbolposition, performing on inverse symbol transform on said detectedsymbol, and obtaining said detection result.
 43. The watermark detectionapparatus as claimed in claim 37, wherein said watermark detectionmeans, comprises: means for outputting a pixel block cut from saiddetected object image by cyclic shift of said cut pixel block, accordingto said offset information.
 44. The watermark detection apparatus asclaimed in claim 37, wherein said watermark detection means, comprises:means for cutting pixel blocks of N×N pixels from said detected objectimage when a size of said detected object image is equal to or greaterthan N×N pixels; means for, when the size of said detected object imageis smaller than N ×N pixels, determining an average pixel value for aportion of said detected object image included when an N×N size pixelblocks, filling a remaining empty portion of said N ×N size pixel blockwith said average pixel value, and generating a first pixel block; andmeans for performing cyclic shift of said first pixel block andoutputting said cyclic shifted first pixel block as a pixel block. 45.The watermark detection apparatus as claimed in claim 37, wherein saidwatermark detection means, comprises: means for dividing said detectedobject image into a pixel block from a position corresponding to saidoffset information; means for performing a discrete Fourier transform onsaid a divided pixel block and generating a detected object coefficientmatrix; means for generating a detected object sequence from saiddetected object component position information and said detected objectcoefficient matrix; means for generating symbol detection informationfrom said detected object sequence and said key; and means foroutputting a detection result corresponding to said symbol detectioninformation.
 46. The watermark detection apparatus as claimed in claim37, wherein said watermark detection means, comprises: means fordividing said detected object image into pixel blocks and performingcyclic-shift of said pixel blocks, according to said offset information;means for performing a discrete Fourier transform on said pixel blockthat has undergone said cyclic-shift, and generating a detected objectcoefficient matrix; means for generating a detected object sequence fromsaid detected object component position information and said detectedobject coefficient matrix; means for generating symbol detectioninformation from said detected object sequence and said key; means forgenerating each detected symbol from said symbol detection information;and means for detecting a watermark from said each detected symbol. 47.The watermark detection apparatus as claimed in claim 37, wherein saidwatermark detection means, comprises: means for dividing said detectedobject image into pixel blocks, and performing cyclic shift of saidpixel blocks, according to the offset information, wherein when pixelblocks around the edges of the detected object image contain emptyportions, the empty portions are filled with an average pixel value;means for performing a discrete Fourier transform on said pixel blockand generating a detected object coefficient matrix; means forgenerating a detected object sequence from said detected objectcomponent position information and said detected object coefficientmatrix; means for generating symbol detection information from saiddetected object sequence and said key; and means for generating eachdetected symbol from said symbol detection information.
 48. Thewatermark detection apparatus as claimed in claim 37, wherein saidposition marker sequence generation means, comprises: means for using anoffset to divide said detected object image into pixel blocks; and meansfor outputting an additional block, which is the sum of correspondingpixel values of said pixel blocks, as a pixel block.
 49. The watermarkdetection apparatus as claimed in claim 37, wherein said position markersequence generation means, comprises: means for dividing said detectedobject image into blocks, and means for generating an additional blockby adding corresponding pixel values of said divided blocks, using anoffset to perform cyclic shift of said additional block, and generatingsaid cyclic shifted additional block as a pixel block.
 50. The watermarkdetection apparatus as claimed in claim 48, wherein said position markersequence generation means, comprises: means for dividing said detectedobject image into blocks and, when a block around the edge of saiddetected object image contains an empty portion, determining an averagevalue of pixel values of the portion of the block including detectedobject image, and filling said empty portion with said average value;means for generating an additional block by adding corresponding pixelvalues of said divided blocks; and means for using an offset to performcyclic shift of said additional block and outputting said cyclic shiftedadditional block as a pixel block.
 51. The watermark detection apparatusas claimed in claim 40, wherein said position marker sequence generationmeans, further comprises: means for changing said detected objectsequence so that an average value of said detected object sequence iszero.
 52. The watermark detection apparatus as claimed in claim 41,wherein said watermark detection means, further comprises: means forchanging said detected object sequence so that an average value of saiddetected object sequence is zero.
 53. The watermark detection apparatusas claimed in claim 40, wherein said position marker detection means,comprises: means for determining a maximum value of said position markerdetection information, and when said maximum value is smaller than arequired threshold value, outputting offset-detection failureinformation, and when said maximum value is equal to or greater thansaid required threshold value, outputting said offset informationcorresponding to said maximum value.
 54. The watermark detectionapparatus as claimed in claim 37, wherein said watermark detectionmeans, comprises: means for dividing symbol detection information foreach symbol position, and generating a sequence for each symbolposition; means for determining a maximum value of said sequence forsaid each symbol positions, and when said maximum value is smaller thana required threshold value, outputting watermark-detection failureinformation, and when said maximum value is equal to or greater thansaid required threshold value, detecting a symbol corresponding to saidmaximum value; and means for converting from said detected symbol into awatermark expression.
 55. The watermark detection apparatus as claimedin claim 54, wherein said required threshold value is determined on thebasis of a value of a normal distribution function having an average of0 and a variance of
 1. 56. A watermark detection apparatus for detectingan embedded watermark in a detected object image, which watermark cannotbe sensed visually, the apparatus comprising: detected object componentspecification means for generating detected object component positioninformation from key; position marker sequence generation means forgenerating a position marker sequence from said key; position markerdetection means for using position marker detection information togeneration offset information that expresses the degree to which a startpoint an embedded watermark pattern is displaced from a start point of apixel block cut from said detected object image; and watermark detectionmeans for using said offset information to detect a watermark embeddedin said pixel block.
 57. The watermark detection apparatus as claimed inclaim 56, wherein said detected object component specification means,comprises: means for generating a random number sequence that has saidkey as an initial value; and means for using said random number sequenceas an basis for generating said detected object component positioninformation having the same length as the length of an embeddingsequence.
 58. The watermark detection apparatus as claimed in claim 56,wherein said position marker sequence generation means, comprises: meansfor generating a 0′th spread sequence having said key as the initialvalue, and outputting spread sequence as a position marker sequence. 59.The watermark detection apparatus as claimed in claim 56, wherein saidposition marker detection means, comprises: means for cutting a pixelblock of a size N×N pixels from said detected object image using saiddetected object component position information and said position markersequence means for performing a discrete Fourier transform on said pixelblock and generating a detected object coefficient matrix; means forgenerating a detected object sequence from said offset information, saiddetected object coefficient matrix and said detected object componentposition information; and means for grouping correlation values for saidposition marker sequence and said detected object sequence andgenerating said them position marker detection information.
 60. Thewatermark detection apparatus as claimed in claim 56, wherein saidwatermark detection means, comprises: means for cutting a pixel blockfrom said detected object image, using said detected object componentposition information, said offset information and said key; means forperforming a discrete Fourier transform on said pixel block andgenerating a detected object coefficient matrix; means for generating adetected object sequence from said offset information, said detectedobject coefficient matrix and said detected object component positioninformation; means for generating symbol detection information from avalue of a correlation between said detected object sequence and asequence generated from said key and symbol candidate information; meansfor using each symbol position of said symbol detection information sthe basis for detecting a symbol when the value of the correlation ismaximum; and means for outputting a result of conversion of saiddetected symbol into a watermark format.
 61. The watermark detectionapparatus as claimed in claim 56, wherein said position marker sequencegeneration means comprises: means for, when a pixel block of a size ofN×N pixels has been-cut from said detected object image, in a case saidpixel block has an empty portion, determining an average of pixel valuesof a portion of said pixel of said pixel block including said detectedobject image, and filling said empty portion with said average value.62. The watermark detection apparatus as claimed in claim 56, whereinsaid watermark detection means comprises: means for dividing a pixelblock from said detected object image; means for performing a discreteFourier transform on said pixel block and generating a detected objectcoefficient matrix; means for generating a detected object sequence fromsaid offset information, said detected object coefficient matrix andsaid detected object component position component position information;means for generating a detected symbol from said detected objectsequence and said key; and means for detecting a watermark from saiddetected symbol.
 63. The watermark detection apparatus as claimed inclaim 56, wherein said watermark detection means comprises: means for,when a pixel block of a size of N×N pixels size has been cut from saiddetected object image, in a case said pixel block has an empty portion,determining an average of pixel values of a portion of said pixel ofsaid pixel block including said detected object image, and filling saidempty portion with said average value.
 64. The watermark detectionapparatus as claimed in claim 56, wherein said watermark detection meansand said position marker sequence generation means comprises: means fordividing said detected object image into blocks of N×N pixel size; andmeans for outputting an additional block, which is the sum of respectivepixel values for all blocks, as a pixel block.
 65. The watermarkdetection apparatus as claimed in claim 64, wherein said watermarkdetection means and said position marker sequence generation meanscomprises: means for, when a pixel block of a size of N×N pixels sizehas been cut from said detected object image, in a case said pixel blockhas an empty portion, determining an average of pixel values of aportion of said pixel of said pixel block including said detected objectimage, and filling said empty portion with said average value.
 66. Thewatermark detection apparatus as claimed in claim 59, wherein saidposition marker sequence generation means comprises: means for changingsaid detected object sequence so that an average value of said detectedobject sequence is zero.
 67. The watermark detection apparatus asclaimed in claim 60, wherein said watermark detection means, comprising:means for changing said detected object sequence so that an averagevalue of said detected object sequence is zero.
 68. The watermarkdetection apparatus as claimed in claim 56, wherein said position markerdetection means, comprising: means for determining a maximum value ofsaid position marker detection information; means for outputting offsetdetection failure information when a maximum of said position markerdetection information is smaller than a required threshold value, andoutputting said offset information when said maximum value is equal toor larger than said required threshold value.
 69. The watermarkdetection apparatus as claimed in claim 60, wherein said watermarkdetection means further comprises: means for dividing, for each symbolposition, said symbol detection information generated from said detectedobject sequence and said key; means for determining a maximum value of asequence for each symbol position; and means for outputting watermarkdetection failure information when said maximum value is smaller than arequired threshold value, and outputting a symbol candidate when saidmaximum value is equal to or larger than said required threshold value.70. The watermark detection apparatus as claimed in claim 69, whereinsaid required threshold value is determined on the basis of a value of anormal distribution function that having a average of 0 and a varianceof
 1. 71. A storage medium that stores a watermark detection programthat performs the detection of a watermark embedded in a detected objectimage which watermark cannot be sensed visually, comprising: a detectedobject component specification process for generating detected objectcomponent position information from key; a position marker sequencegeneration process for generating a position marker sequence from saidkey; a position marker detection process for detecting said positionmarker sequence, and extracting offset information when a start point ofthe embedded watermark is in agreement with a start point of a pixelblock cut from the detected object image; and a watermark detectionprocess for detecting said embedded watermark from said pixel block cutfrom said detected object image on the basis of said offset information.72. The storage medium that stores a watermark detection program asclaimed in claim 71, wherein said detected object componentspecification process comprises: a process for generating a randomnumber sequence that has said key as an initial value; and a process forgenerating said detected object component position information from saidrandom number sequence.
 73. The storage medium that stores a watermarkdetection program as claimed in claim 71, wherein said detected objectspecification process, comprising: a process for generating a 0′thspread sequence taking said key as the initial value, and outputtingsaid spread sequence as said position marker sequence.
 74. The storagemedium that stores a watermark detection program as claimed in claim 71,wherein said position marker detection process, comprising: a processfor generating offset candidate information, a process for cutting apixel block from a position of said detected object image, whichposition is determined by said offset candidate information; a processfor performing a discrete Fourier transform on said pixel block andgenerating a detected object coefficient matrix, a process forgenerating a detected object sequence from said detected objectcomponent position information and said detected object coefficientmatrix, a process for grouping said offset candidate information andcorrelation value for said position marker sequence and said detectedobject sequence and generating position marker detection information,and a process for extracting, as said offset information, offsetcandidate information when the correlation value between said positionmarker sequence and said detected object sequence is maximum.
 75. Thestorage medium that stores a watermark detection program as claimed inclaim 71, wherein said watermark detection process, comprising: aprocess for cutting a pixel block of N×N pixels from a position of saiddetected object images, which position has undergone paralleldisplacement by the amount of said offset candidate information; aprocess for performing a discrete Fourier transform on said pixel blockand generating a detected object coefficient matrix; a process forgenerating a detected object information from said detected objectcomponent position information and said detected object coefficientmatrix; a process for generating symbol detection information from saiddetected object sequence and said key; a process for generating eachdetected symbol from said symbol detection information; and a processfor outputting as a watermark, detection result from each detectedsymbol.
 76. The storage medium that stores a watermark detection programas claimed in claim 75, wherein said watermark detection process,further comprising: a process for generating a sequence for each symbolposition of said symbol detection information; and a process forselecting, as the detected symbol, a symbol candidate having maximumvalue in the sequence for said each symbol position, performing aninverse symbol transform on said detected symbol, and obtaining saiddetection result.
 77. The storage medium that stores a watermarkdetection program as claimed in claim 71, wherein said watermarkdetection process, comprising: a process for outputting a pixel blockcut from said detected object image by cyclic shift of said cut pixelblock, according said offset.
 78. The storage medium that stores awatermark detection program as claimed in claim 71, wherein saidwatermark detection process, comprising: a process for cutting pixelblocks of N×N pixels from said detected object image when said detectedobject image is of an N×N size or more, a process for when said detectedobject image is smaller than said N×N size, determining an average pixelvalue for a portion of said detected object image that would have beenincluded if said N×N size of said detected object image had been cut,filling said average pixel value into a portion that does not make upsaid N×N size, and generating a pixel block; and a process forperforming cyclic shift of said cut block and outputting a detectionresult.
 79. The storage medium that stores a watermark detection programas claimed in claim 71, wherein said watermark detection process,comprising: a process for dividing said detected object image into apixel block from a position corresponding to said offset information; aprocess for performing a discrete Fourier transform on said dividedpixel block and generating a detected object coefficient matrix; aprocess for generating a detected object sequence from said detectedobject component position information and said detected objectcoefficient matrix; a process for generating symbol detectioninformation from said detected object sequence and said key; and aprocess for outputting a detection result corresponding to said symboldetection information.
 80. The storage medium that stores a watermarkdetection program as claimed in claim 71, wherein said watermarkdetection process, comprising: a process for dividing said detectedobject image into pixel blocks and performing cyclic shift of said pixelblocks according to said offset information; a process for performing adiscrete Fourier transform on said pixel blocks that have undergone saidcyclic shift, and generating a detected object sequence matrix; aprocess for generating a detected object sequence from said detectedobject component position information and said detected objectcoefficient matrix; a process for generating symbol detectioninformation from said detected object sequence and said key; a processfor generating each detected symbol from said symbol detectioninformation, and a process for detecting a watermark from said eachdetected symbol.
 81. The storage medium that stores a watermarkdetection program as claimed in claim 71, wherein said watermarkdetection process, comprising: a process for dividing said detectedobject image into pixel blocks and performing cyclic shift of said pixelblocks according to the offset information, wherein portions around theedges of the detected object image that do not make up an N×N size pixelblock, are filled with an average pixel value; a process for performinga discrete Fourier transform on said pixel block and generating adetected object coefficient matrix; a process for generating a detectedobject sequence from said detected object component position informationand said detected object coefficient matrix; a process for generatingsymbol detection information from said detected object sequence and saidkey; and a process for generating each detected symbol from said symboldetection information.
 82. The storage medium that stores a watermarkdetection program as claimed in claim 71, wherein said position markergeneration process, comprising: a process for using an offset to dividesaid detected object image into pixel blocks; and a process foroutputting an additional block , which is the sum of corresponding pixelvalue of said pixel blocks, as pixel block.
 83. The storage medium thatstores a watermark detection program as claimed in claim 71, whereinsaid position marker generation process, comprising: a process fordividing said detected object image into blocks; and a process formaking a block obtained by adding pixel values of said divided blocks,into an additional block, performing cyclic shift of said additionalblock by an offset, and generation a pixel block.
 84. The storage mediumthat stores a watermark detection program as claimed in claim 82,wherein said position marker generation process; comprising: a processfor dividing said detected object image into blocks and, when a blockaround the edge of said detected object image contains an empty portion,determining an average value of pixel values of the portion of the blockincluding detected object image, and filling said empty portion withsaid average value; a process for generating an additional block byadding corresponding pixel values of said divided blocks; and a processfor using an offset to perform cyclic shift of said additional block andgenerating a pixel block.
 85. The storage medium that stores a watermarkdetection program as claimed in claim 74, wherein said position markergeneration process, further comprising: a process for changing saiddetected object sequence so that an average value of said detectedobject sequence is zero.
 86. The storage medium that stores a watermarkdetection program as claimed in claim 80, wherein said watermarkdetection process, further comprising: a process for changing saiddetected object sequence so that an average value of said detectedobject sequence is zero.
 87. The storage medium that stores a watermarkdetection program as claimed in claim 81, wherein said watermarkdetection process, further comprising: a process for changing saiddetected object sequence so that an average value of said detectedobject sequence is zero.
 88. The storage medium that stores a watermarkdetection program as claimed in claim 74, wherein said position markerdetection process, comprising: a process for determining a maximum valueof said position marker detection information, and when maximum value issmaller than a required threshold value, outputting offset detectionfailure information, and when said maximum value is equal to or greaterthan said required threshold value, outputting said offset informationcorresponding to said maximum value.
 89. The storage medium that storesa watermark detection program as claimed in claim 75, wherein saidwatermark detection process, comprising: a process for dividing symboldetection information for each symbol position and generating a sequencefor each of said symbol positions, a process for determining a maximumvalue of said sequence for each symbol position, and when said maximumvalue is smaller than a required threshold value outputting watermarkdetection failure information, and when said maximum value is equal toor greater than said required threshold value, detecting a symbolcorresponding to said maximum value; and a process for converting fromsaid detected symbol into a watermark expression.
 90. The storage mediumthat stores a watermark detection program as claimed in claim 89,wherein said required threshold value is determined on the basis of avalue of normal distribution function having an average of 0 and avariance of
 1. 91. A storage medium that stores a watermark detectionprogram that detects a watermark, in a detected object image whichwatermark is imperceptible digital data visually, the program comprises:a detected object component specification process for generatingdetected object component position information from a key; a positionmarker sequence generation process for generating a position makersequence from the key; a position marker detection process for usingposition marker detection information to generation offset informationthat expresses the degree to which a start point of an embeddedwatermark pattern is displaced from a start point of a pixel block cutfrom said detected object image; and a watermark detection means forusing said offset information to detect a watermark embedded in saidpixel block.
 92. The storage medium that stores a watermark detectionprogram as claimed in claim 91, wherein said detected object componentspecification process comprises; a process for generating a randomnumber sequence that has said key as an initial value; and a process forgenerating said detected object component position information from saidrandom number sequence.
 93. The storage medium that stores a watermarkdetection program as claimed in claim 91, wherein said position markersequence generation process comprises; a process for generating a 0′thspread sequence taking said key as an initial value, and outputting saidspread sequence as said position marker sequence.
 94. The storage mediumthat stores a watermark detection program as claimed in claim 91,wherein said position marker sequence generation process comprises; aprocess for generating offset candidate information, and cutting a pixelblock of a size of N×N pixels from said detected object image using saiddetected object component position information and said position markersequence; a process for performing a discrete Fourier transform on saidpixel block and generating a detected object coefficient matrix; aprocess for generating a detected object sequence from said detectedobject component position information and said detected objectcoefficient matrix; and a process for grouping correlation value forsaid position marker sequence and said detected object sequence andgenerating said position marker detection information.
 95. The storagemedium that stores a watermark detection program as claimed in claim 91,wherein said watermark detection process comprises; a process forcutting a pixel block of N×N pixels from a position of said detectedobject image, which position has undergone parallel displacement by theamount of said offset candidate information; a process for performing adiscrete Fourier transform on said pixel block and generating a detectedobject coefficient matrix, a process for generating a detected objectsequence from said offset information, said detected object coefficientmatrix and said detected object component position information; aprocess for generating a symbol detection information from a value of acorrelation between said detected object sequence and a sequencegenerated from said key and symbol candidate information; a process forusing each symbol position of said symbol detection information as thebasis for detecting a symbol when the value of the correlation ismaximum; and a process for outputting a result of conversion of saiddetected symbol into a watermark format.
 96. The storage medium thatstores a watermark detection program as claimed in claim 94, whereinsaid position marker sequence generation process comprises; a processfor, when a pixel block of N×N pixel size has been cut from saiddetected object image, in a case said pixel block has an empty portion,determining an average of pixel values of a portion of said pixel blockincluding said detected object image, and filling said empty portionwith said average value.
 97. The storage medium that stores a watermarkdetection program as claimed in claim 91, wherein said watermarkdetection process comprises; a process for dividing a pixel block fromsaid detected object image; a process for performing a discrete Fouriertransform on said pixel block and generating a detected objectcoefficient matrix; a process for generating a detected object sequencefrom said offset information, said detected object component positioninformation and said detected object coefficient matrix; a process forgenerating a detected symbol from said detected object sequence and saidkey; and a process for detecting a watermark from said detected symbol.98. The storage medium that stores a watermark detection program asclaimed in claim 91, wherein said watermark detection process comprises;a process for, when a pixel block of N×N pixel size has been cut fromsaid detected object image, in a case said pixel block has an emptyportion, determining an average of pixel values of a portion of saidpixel block including said detected object image, and filling said emptyportion with said average value.
 99. The storage medium that stores awatermark detection program as claimed in claim 91, wherein saidposition marker sequence generation process comprises; a process for,when a pixel block of N×N pixel size has been cut from said detectedobject image, in a case said pixel block has an empty portion,determining an average of pixel values of a portion of said pixel blockincluding said detected object image, and filling said empty portionwith said average value.
 100. The storage medium that stores a watermarkdetection program as claimed in claim 91, wherein said watermarkdetection process, comprising; a process for dividing said detectedobject image into blocks of N×N pixel size; and a process foroutputting, an additional block which is the sum of respective pixelvalues for all blocks, as a pixel block.
 101. The storage medium thatstores a watermark detection program as claimed in claim 91, whereinsaid watermark detection process comprises; a process for, when a pixelblock of N×N pixel size has been cut from said detected object image, ina case said pixel block has an empty portion, determining an average ofpixel values of a portion of said pixel block including said detectedobject image, and filling said empty portion with said average value.102. The storage medium that stores a watermark detection program asclaimed in claim 91, wherein said position marker sequence generationprocess, comprising; a process for, when a pixel block of N×N pixel sizehas been cut from said detected object image, in a case said pixel blockhas an empty portion, determining an average of pixel values of aportion of said pixel block including said detected object image, andfilling said empty portion with said average value.
 103. The storagemedium that stores a watermark detection program as claimed in claim102, wherein said position marker sequence generation process furthercomprises; a process for changing said detected object sequence so thatan average value of said detected object sequence is zero.
 104. Thestorage medium that stores a watermark detection program as claimed inclaim 101, wherein said watermark detection process further comprises; aprocess for changing said detected object sequence so that an averagevalue of said detected object sequence is zero.
 105. The storage mediumthat stores a watermark detection program as claimed in claim 91,wherein said position marker detection process comprises; a process fordetermining a maximum value of said a position marker detectioninformation; a process for outputting offset detection failureinformation when a maximum value of said position marker detectioninformation is smaller than a required threshold value, and outputtingsaid offset information when said maximum value is equal to or largerthan said required threshold value.
 106. The storage medium that storesa watermark detection program as claimed in claim 91, wherein saidwatermark detection process further comprises; a process for dividing,for each symbol position, symbol detection information generated fromsaid detected object sequence and said key; a process for determiningthe maximum value of a sequence for each symbol position, for eachsymbol position, and a process for outputting failure for detect of awatermark when said maximum value is smaller than a required thresholdvalue; and a process for outputting a symbol candidate when there issaid maximum value, in cases when said maximum value is equal to orlarger than a required threshold value.
 107. The storage medium thatstores a watermark detection program as claimed in claim 95, whereinsaid watermark detection process comprises; a process for dividing foreach symbol position, symbol detection information generated from saiddetected object sequence and said key; a process for determining themaximum value of a sequence for each symbol position, for each symbolposition; and a process for outputting failure for detect of a watermarkwhen said maximum value is smaller than a required threshold value, anda process for outputting a symbol candidate when there is said maximumvalue, in cases when said maximum value is equal to or larger thanrequired threshold value.
 108. The storage medium that stores awatermark detection program as claimed in claim 107, wherein saidthreshold value uses a threshold value determined on the basis of avalue of a distribution function that is a normal distribution having anaverage of 0 and a variance of
 1. 109. The storage medium that stores awatermark detection program as claimed in claim 108, wherein saidthreshold value uses a threshold value determined on the basis of avalue of a distribution function that is a normal distribution having anaverage of 0 and a variance of 1.